# ElectronicsInfoline: every lesson

> 262 lessons, each with its canonical URL and description.

## School of Fundamentals

### Electricity Basics

- [Analog vs Digital Signals](https://www.electronicsinfoline.com/fundamentals/electricity-basics/analog-vs-digital/): An analog signal can take any value; a digital one is read as a small set of levels. What quantisation and sampling cost, and what noise immunity buys.
- [Batteries in Series & Parallel](https://www.electronicsinfoline.com/fundamentals/electricity-basics/battery-series-parallel/): Series stacking adds voltage and internal resistance; parallel connection adds capacity and current capability. What each arrangement buys, and costs.
- [What Is a Circuit?](https://www.electronicsinfoline.com/fundamentals/electricity-basics/circuit-concept/): A circuit is a complete loop that carries charge from a source, through a load, and back again. What every circuit needs, and why a break stops it all.
- [Conductors & Insulators](https://www.electronicsinfoline.com/fundamentals/electricity-basics/conductors-insulators/): Conductors let charge move freely, insulators hold it in place, and the gap between them spans roughly twenty-four orders of magnitude. Why materials differ.
- [Current Limiting](https://www.electronicsinfoline.com/fundamentals/electricity-basics/current-limiting/): Some loads will take more current than they survive, so something must set it. Series resistors, active limiters and protection devices, and what each costs.
- [Current Sources](https://www.electronicsinfoline.com/fundamentals/electricity-basics/current-source/): A current source sets the current and lets the load decide the voltage. The dual of a voltage source, with compliance limits instead of a current limit.
- [DC vs AC](https://www.electronicsinfoline.com/fundamentals/electricity-basics/dc-vs-ac/): Direct current flows one way; alternating current reverses many times a second. Why both exist, what RMS really means, and where each one belongs.
- [Electric Charge](https://www.electronicsinfoline.com/fundamentals/electricity-basics/electric-charge/): Electric charge is the property that makes electricity possible. What a coulomb counts, how charge becomes current, and why charge comes in indivisible steps.
- [Electric Current](https://www.electronicsinfoline.com/fundamentals/electricity-basics/electric-current/): Electric current is the rate at which charge flows. What an ampere measures, how to measure one without destroying a meter, and what actually moves in a wire.
- [Electrical Energy & the kWh](https://www.electronicsinfoline.com/fundamentals/electricity-basics/electrical-energy/): Energy is power multiplied by time, measured in joules — or, on a bill, in kilowatt-hours. Why batteries are rated in mAh, and what that hides.
- [Electrical Power](https://www.electronicsinfoline.com/fundamentals/electricity-basics/electrical-power/): Power is the rate at which electrical energy is converted, measured in watts. The three formulas, why they are one relationship, and where the heat goes.
- [Electrical Safety Fundamentals](https://www.electronicsinfoline.com/fundamentals/electricity-basics/electrical-safety/): Current through the body does the damage, and mains can supply far more than enough. The habits, the equipment and the order of operations that keep you alive.
- [Electrons & Atomic Structure](https://www.electronicsinfoline.com/fundamentals/electricity-basics/electron-atomic-structure/): How atoms hold their electrons, why some materials release them freely, and how energy bands turn that into conductors, insulators and semiconductors.
- [Scientific & Engineering Notation](https://www.electronicsinfoline.com/fundamentals/electricity-basics/engineering-notation/): How powers of ten tame very large and very small values, why engineers keep exponents in multiples of three, and how significant figures decide the digits.
- [Electrostatic Discharge (ESD) Basics](https://www.electronicsinfoline.com/fundamentals/electricity-basics/esd-basics/): Electrostatic discharge destroys parts without leaving a mark. Where static comes from, what it does to a device, and the bench routine that prevents it.
- [Ground & Reference Points](https://www.electronicsinfoline.com/fundamentals/electricity-basics/ground-reference/): Ground is the node a circuit agrees to call zero volts. Why the choice is arbitrary, why the copper is not, and what happens when two grounds disagree.
- [Loads & Loading](https://www.electronicsinfoline.com/fundamentals/electricity-basics/load-concept/): The load is whatever draws current from a source, and connecting one changes what the source delivers. How loading works, and when it wrecks a measurement.
- [Ohm's Law](https://www.electronicsinfoline.com/fundamentals/electricity-basics/ohms-law/): Ohm's law (V = IR) at four depths — intuition, practical use, the physics behind it, and where it breaks — with worked, code-verified examples.
- [Open Circuits & Short Circuits](https://www.electronicsinfoline.com/fundamentals/electricity-basics/open-short-circuit/): An open circuit is a break where there should be a path; a short is a path where there should be none. Both are Ohm's law taken to an extreme.
- [Resistance](https://www.electronicsinfoline.com/fundamentals/electricity-basics/resistance/): Resistance measures how strongly something opposes current, in ohms. Where it comes from, how it is measured, and why the number on the part is a band.
- [Resistivity & Conductance](https://www.electronicsinfoline.com/fundamentals/electricity-basics/resistivity-conductance/): Resistivity belongs to the material and resistance to the object. Conductance is the reciprocal view, and it is the one that makes parallel paths easy.
- [Schematic Diagrams & Symbols](https://www.electronicsinfoline.com/fundamentals/electricity-basics/schematic-symbols/): A schematic records what connects to what, not where anything sits. How to read the symbols, the designators and the conventions that make a diagram usable.
- [Semiconductor Materials](https://www.electronicsinfoline.com/fundamentals/electricity-basics/semiconductor-materials/): Semiconductors conduct badly on purpose, and their conductivity can be set by adding impurities. Why silicon won, and what the band gap actually decides.
- [SI Units & Engineering Prefixes](https://www.electronicsinfoline.com/fundamentals/electricity-basics/si-units-prefixes/): What kilo, milli, micro, nano and pico actually mean, how to convert between them without losing a factor of a thousand, and the SI style rules that matter.
- [Temperature Effects on Resistance](https://www.electronicsinfoline.com/fundamentals/electricity-basics/temperature-effects-resistance/): Metals grow more resistive as they heat and semiconductors less. The linear model, where it holds, and how resistance becomes a thermometer.
- [Voltage](https://www.electronicsinfoline.com/fundamentals/electricity-basics/voltage/): Voltage is energy per unit charge — the push behind every current. What a volt measures, why it always needs two points, and why a loaded supply sags.
- [Voltage Sources (Ideal & Real)](https://www.electronicsinfoline.com/fundamentals/electricity-basics/voltage-source/): An ideal voltage source holds its voltage whatever current is drawn. Real ones sag, because every source has internal resistance, and that resistance matters.
- [Wire Resistance & Voltage Drop](https://www.electronicsinfoline.com/fundamentals/electricity-basics/wire-resistance-voltage-drop/): Wire has resistance, so current through it costs voltage the load never sees. How to size a conductor to a drop budget rather than to a current rating.

### DC Circuit Analysis

- [Attenuators](https://www.electronicsinfoline.com/fundamentals/dc-circuits/attenuators/): A divider carrying a specification: a reduction stated in decibels and a defined impedance at each port, built as an L-pad, a T-pad or a Pi-pad.
- [Circuit Simulation (SPICE) Basics](https://www.electronicsinfoline.com/fundamentals/dc-circuits/circuit-simulation-spice/): SPICE reduces a circuit to a netlist, writes one current balance equation per node and solves it: reference node 0, floating nodes, and which analysis to run.
- [The Current Divider](https://www.electronicsinfoline.com/fundamentals/dc-circuits/current-divider/): A current divider splits a known total current between two parallel branches, and each branch's share is set by the resistance of the opposite branch.
- [Troubleshooting DC Circuits](https://www.electronicsinfoline.com/fundamentals/dc-circuits/dc-troubleshooting/): Measure voltage first, powered and in circuit, halve the suspect region with each reading, and read an open, a short or a resistive joint from the drops.
- [Delta-Wye (Δ-Y) Transformation](https://www.electronicsinfoline.com/fundamentals/dc-circuits/delta-wye-transformation/): Exchange a triangle of three resistances for the equivalent star, or the star back for the triangle, and a bridge that will not reduce opens up.
- [Dependent (Controlled) Sources](https://www.electronicsinfoline.com/fundamentals/dc-circuits/dependent-sources/): A dependent source takes its value from a voltage or current elsewhere in the circuit. The four types, their four gain units, and the deactivation rule.
- [Kirchhoff's Current Law (KCL)](https://www.electronicsinfoline.com/fundamentals/dc-circuits/kcl/): The currents entering any node of a circuit sum to the currents leaving it, because charge cannot pile up at a junction: signs, supernodes, limits.
- [Kirchhoff's Voltage Law (KVL)](https://www.electronicsinfoline.com/fundamentals/dc-circuits/kvl/): The signed voltages around any closed loop sum to zero: traversal direction, sign convention, the energy argument behind it, and where changing flux breaks it.
- [Ladder Networks (incl. R-2R)](https://www.electronicsinfoline.com/fundamentals/dc-circuits/ladder-networks/): A ladder network repeats one series-and-shunt section, so it collapses from the far end inwards; R-2R reproduces itself at every rung and halves each bit.
- [Maximum Power Transfer Theorem](https://www.electronicsinfoline.com/fundamentals/dc-circuits/maximum-power-transfer/): A source with a fixed internal resistance gives up the most power to a load equal to it: where that peak sits, how flat it is, and what it costs.
- [Mesh Analysis](https://www.electronicsinfoline.com/fundamentals/dc-circuits/mesh-analysis/): Give every window of a planar circuit its own circulating current, write a loop equation round each, and solve; a shared branch carries the difference.
- [Nodal Analysis](https://www.electronicsinfoline.com/fundamentals/dc-circuits/nodal-analysis/): Choose a reference node, give every other node an unknown voltage, write current balance at each one, and solve; a floating source ties two nodes together.
- [Norton's Theorem](https://www.electronicsinfoline.com/fundamentals/dc-circuits/nortons-theorem/): Any linear two-terminal network behaves at its terminals like one current source in parallel with one resistance: how to find both, and when to use it.
- [Parallel Circuits](https://www.electronicsinfoline.com/fundamentals/dc-circuits/parallel-circuits/): Branches wired in parallel all sit at one voltage and their currents add, so the group conducts better than any single branch and its resistance drops.
- [Power Dissipation in Resistive Circuits](https://www.electronicsinfoline.com/fundamentals/dc-circuits/power-dissipation/): Total power into a resistive network equals the total dissipated, but the share each element takes is uneven and the part nearest its rating fails first.
- [Series Circuits](https://www.electronicsinfoline.com/fundamentals/dc-circuits/series-circuits/): Components joined end to end carry one common current, their voltage drops add up to the source voltage, and their resistances add to give the chain total.
- [Series-Parallel Networks](https://www.electronicsinfoline.com/fundamentals/dc-circuits/series-parallel-networks/): Reduce a resistor network one series or parallel pair at a time until a single equivalent remains, then work back outwards to recover every branch current.
- [Source Transformation](https://www.electronicsinfoline.com/fundamentals/dc-circuits/source-transformation/): Swapping a voltage source and its series resistance for a current source across that same resistance: both directions, iterating it, and what it gets wrong.
- [Superposition Theorem](https://www.electronicsinfoline.com/fundamentals/dc-circuits/superposition-theorem/): In a linear circuit the response to several sources is the sum of the responses to each acting alone: the procedure, the proof from linearity, and the limits.
- [Thévenin's Theorem](https://www.electronicsinfoline.com/fundamentals/dc-circuits/thevenins-theorem/): Any linear two-terminal network behaves at its terminals like one voltage source in series with one resistance: how to find both, and where it stops.
- [The Voltage Divider](https://www.electronicsinfoline.com/fundamentals/dc-circuits/voltage-divider/): Two series resistances set a tap voltage from their ratio alone, until something is connected to it: design, loading error and the Thevenin equivalent.
- [The Wheatstone Bridge](https://www.electronicsinfoline.com/fundamentals/dc-circuits/wheatstone-bridge/): Two voltage dividers across one supply, compared against each other: the balance condition, the output either side of it, null mode and deflection mode.

### Capacitance, Inductance & Transients

- [Capacitance](https://www.electronicsinfoline.com/fundamentals/energy-storage/capacitance/): Capacitance is the charge a component takes on per volt applied. What a farad really is, why real parts are tiny fractions of one, and how to pick a value.
- [Capacitor Charging & Discharging](https://www.electronicsinfoline.com/fundamentals/energy-storage/capacitor-charge-discharge/): What a capacitor does while its voltage is moving: the exponential curve, the current the resistor sets, and why a charged reservoir stays dangerous.
- [Capacitors in Series & Parallel](https://www.electronicsinfoline.com/fundamentals/energy-storage/capacitors-series-parallel/): Capacitors combine the opposite way round to resistors: parallel adds, series reduces. How to work a network, and what series voltage division really does.
- [Dielectrics & Permittivity](https://www.electronicsinfoline.com/fundamentals/energy-storage/dielectrics/): The insulator between a capacitor's plates does the real work: permittivity multiplies the value, breakdown strength sets the rating, losses set the rest.
- [Energy Stored in a Capacitor](https://www.electronicsinfoline.com/fundamentals/energy-storage/energy-stored-capacitor/): A charged capacitor stores energy as the square of its voltage. Where the half comes from, why charging is only 50 % efficient, and what that energy can do.
- [Energy Stored in an Inductor](https://www.electronicsinfoline.com/fundamentals/energy-storage/energy-stored-inductor/): An inductor stores energy in its magnetic field, as the square of its current. Why that energy needs somewhere to go, and what it costs when it is not given it.
- [First-Order Transient Analysis](https://www.electronicsinfoline.com/fundamentals/energy-storage/first-order-transients/): Any circuit with one capacitor or one inductor settles the same way. Find the starting value, the final value and the time constant, and the answer is written.
- [Inductance](https://www.electronicsinfoline.com/fundamentals/energy-storage/inductance/): Inductance is a circuit's opposition to a change of current, in henries. Where it comes from, what it does to a switched circuit, and how to pick a coil.
- [Inductors in Series & Parallel](https://www.electronicsinfoline.com/fundamentals/energy-storage/inductors-series-parallel/): Inductances combine exactly as resistances do, provided the coils share no flux. What coupling does to that rule, and why parallel coils rarely share evenly.
- [Passive RC Integrators & Differentiators](https://www.electronicsinfoline.com/fundamentals/energy-storage/integrator-differentiator-rc/): One resistor, one capacitor, two circuits. Take the output across the capacitor and you integrate; take it across the resistor and you differentiate.
- [Mutual Inductance & Coupling](https://www.electronicsinfoline.com/fundamentals/energy-storage/mutual-inductance/): When two windings share a magnetic field, a current change in one produces a voltage in the other. Coupling coefficient, leakage, and how M is measured.
- [Pulse Response & Rise Time](https://www.electronicsinfoline.com/fundamentals/energy-storage/pulse-response-rise-time/): Rise time is what an RC network does to an edge. Where the 2.2 and the 0.35 come from, and why a scope's own rise time is part of every measurement.
- [The RC Time Constant](https://www.electronicsinfoline.com/fundamentals/energy-storage/rc-time-constant/): The RC time constant (τ = RC) from water-tank intuition to design reality: charging curves, the 63% rule, derivation, and why real timing circuits drift.
- [The RL Time Constant](https://www.electronicsinfoline.com/fundamentals/energy-storage/rl-time-constant/): An RL circuit's time constant is inductance divided by resistance, so more resistance makes it faster. The same exponential as RC, with the roles swapped.
- [Second-Order (RLC) Transients](https://www.electronicsinfoline.com/fundamentals/energy-storage/second-order-transients/): Two energy stores, and the response can ring. Natural frequency, damping ratio and overshoot, and how to place a circuit in the regime you actually want.

### AC Circuits

- [AC Circuit Analysis with Phasors](https://www.electronicsinfoline.com/fundamentals/ac-circuits/ac-circuit-analysis/): Replace every resistance with an impedance at the working frequency and the DC network theorems all carry across to AC, provided each answer keeps its angle.
- [AC Power: Real, Reactive & Apparent](https://www.electronicsinfoline.com/fundamentals/ac-circuits/ac-power/): Real power in watts, reactive power in var and apparent power in volt-amperes: what each one measures, why they form a right triangle, and which sizes a cable.
- [Peak, Peak-to-Peak & Instantaneous Values](https://www.electronicsinfoline.com/fundamentals/ac-circuits/amplitude-measures/): Peak, peak-to-peak, instantaneous and RMS all describe the same sine wave and all give different numbers. Which one a scope reports, and which a meter does.
- [Band-Pass & Band-Stop Filters](https://www.electronicsinfoline.com/fundamentals/ac-circuits/band-pass-stop-filters/): Two corners facing each other keep a band and shed everything outside it, while a resonant branch does the reverse and takes one frequency out of a signal.
- [Bode Plot Basics](https://www.electronicsinfoline.com/fundamentals/ac-circuits/bode-plots/): A Bode plot shows gain in decibels and phase in degrees against a logarithmic frequency axis, so every pole becomes two straight lines crossing at its corner.
- [Capacitive Reactance](https://www.electronicsinfoline.com/fundamentals/ac-circuits/capacitive-reactance/): Capacitive reactance is a capacitor's opposition to alternating current, in ohms. It falls as frequency rises, and unlike resistance it dissipates nothing.
- [Square, Triangle & Other Waveforms](https://www.electronicsinfoline.com/fundamentals/ac-circuits/common-waveforms/): Sine, square, triangle, sawtooth and pulse waveforms compared at one peak value: how the shape changes RMS, crest factor, harmonic content and meter readings.
- [Complex Numbers for Electronics](https://www.electronicsinfoline.com/fundamentals/ac-circuits/complex-numbers-ee/): Why electronics writes j instead of i, how a rectangular pair becomes a magnitude and an angle, and what multiplying by j does to a quantity on the plane.
- [Cutoff Frequency & the -3 dB Point](https://www.electronicsinfoline.com/fundamentals/ac-circuits/cutoff-frequency/): A filter's cutoff frequency is where output power has fallen by half, leaving about seven tenths of the amplitude: the -3 dB point, at 1/(2πRC).
- [The Decibel](https://www.electronicsinfoline.com/fundamentals/ac-circuits/decibel/): The decibel states a ratio as ten times its logarithm for power and twenty times for amplitude, so gains and losses along a signal chain add up.
- [Duty Cycle & PWM Basics](https://www.electronicsinfoline.com/fundamentals/ac-circuits/duty-cycle-pwm-intro/): Duty cycle is the on-time fraction of a switched waveform, and PWM varies it to set power: why the average voltage and the RMS voltage disagree.
- [EMI & EMC Basics](https://www.electronicsinfoline.com/fundamentals/ac-circuits/emi-emc-basics/): Interference needs a source, a coupling path and a victim. The routes it takes, the two things a designer can move, and what a conformity test asks.
- [Fourier Series: an Introduction](https://www.electronicsinfoline.com/fundamentals/ac-circuits/fourier-series-intro/): A repeating waveform written as sines at whole multiples of one frequency: harmonic coefficients, a square wave built up term by term, and the Gibbs overshoot.
- [Frequency & Period](https://www.electronicsinfoline.com/fundamentals/ac-circuits/frequency-period/): Frequency counts cycles per second and period times one cycle, so each is the reciprocal of the other. Angular frequency states the same rate in radians.
- [Ground Loops & Grounding Practice](https://www.electronicsinfoline.com/fundamentals/ac-circuits/ground-loops/): A ground loop lets one circuit's return current cross another circuit's reference. Why shared impedance is the real fault, and which cures are safe to fit.
- [Harmonics](https://www.electronicsinfoline.com/fundamentals/ac-circuits/harmonics/): Harmonics are whole-number multiples of a signal's fundamental frequency: why a square wave carries only odd ones, and why its fundamental tops its peak.
- [Passive High-Pass Filters](https://www.electronicsinfoline.com/fundamentals/ac-circuits/high-pass-filter/): Move the output of an RC pair from the capacitor to the resistor and it blocks DC, climbs twenty decibels a decade, and corners at one over two pi R C.
- [Impedance](https://www.electronicsinfoline.com/fundamentals/ac-circuits/impedance/): Impedance is a circuit's total opposition to alternating current at one frequency: resistance and reactance combined into a magnitude in ohms and an angle.
- [Impedance Matching](https://www.electronicsinfoline.com/fundamentals/ac-circuits/impedance-matching/): Matching a load to its source buys the most power the source can give: transformer ratios, conjugate matching, mismatch loss in decibels, and when to skip it.
- [Inductive Reactance](https://www.electronicsinfoline.com/fundamentals/ac-circuits/inductive-reactance/): Inductive reactance is a coil's opposition to alternating current, in ohms. It rises in direct proportion to frequency, and it dissipates nothing.
- [Passive Low-Pass Filters](https://www.electronicsinfoline.com/fundamentals/ac-circuits/low-pass-filter/): A resistor feeding a shunt capacitor keeps the slow part of a signal and sheds the fast part, losing twenty decibels a decade above its RC corner.
- [Electrical Noise Basics](https://www.electronicsinfoline.com/fundamentals/ac-circuits/noise-basics/): Thermal noise puts a floor under every signal. Where that floor comes from, how resistance and bandwidth move it, and why interference is a separate problem.
- [Parallel RLC Circuits](https://www.electronicsinfoline.com/fundamentals/ac-circuits/parallel-rlc/): A parallel RLC peaks in impedance where a series one collapses: the branch currents cancel instead of the voltages, and more resistance now buys more Q.
- [Phase & Phase Difference](https://www.electronicsinfoline.com/fundamentals/ac-circuits/phase/): Phase fixes where a wave sits in its cycle. Between two waves of one frequency it is a fixed delay, read off a scope and quoted as an angle out of 360.
- [Phasors](https://www.electronicsinfoline.com/fundamentals/ac-circuits/phasors/): A phasor freezes a sinusoid of one frequency into a length and an angle, so voltages that peak at different moments add as arrows and not as plain numbers.
- [Power Factor & Correction](https://www.electronicsinfoline.com/fundamentals/ac-circuits/power-factor/): Why a motor draws more current than its wattage suggests, what a capacitor across its terminals does about that, and how to size one for a target figure.
- [Q Factor & Bandwidth](https://www.electronicsinfoline.com/fundamentals/ac-circuits/q-factor-bandwidth/): Q reads three ways: energy stored against energy lost, centre frequency over bandwidth, and magnification at resonance. All three give one number.
- [Resonance](https://www.electronicsinfoline.com/fundamentals/ac-circuits/resonance/): Resonance is the one frequency where a coil and a capacitor trade all their energy: what fixes it, how tuning moves it, and where it turns up uninvited.
- [RMS Value](https://www.electronicsinfoline.com/fundamentals/ac-circuits/rms-value/): RMS is the steady voltage that would heat a resistor as much as a changing one does, and the reason the divide-by-1.414 shortcut belongs to the sine alone.
- [Series RLC Circuits](https://www.electronicsinfoline.com/fundamentals/ac-circuits/series-rlc/): A series RLC has one frequency where its two reactances cancel, leaving the resistance alone: impedance collapses, current peaks, and Q sets the sharpness.
- [The Sine Wave](https://www.electronicsinfoline.com/fundamentals/ac-circuits/sine-wave/): The sine wave is the shape rotating machinery makes and the only one a linear circuit leaves intact. Peak, period, angular frequency and instantaneous value.
- [Three-Phase Power Basics](https://www.electronicsinfoline.com/fundamentals/ac-circuits/three-phase-basics/): Three voltages a third of a cycle apart: why the line-to-line figure is root three times the phase voltage, how star and delta differ, what the neutral carries.
- [Transfer Functions: an Introduction](https://www.electronicsinfoline.com/fundamentals/ac-circuits/transfer-function-intro/): A transfer function is a circuit's output over its input as a function of the complex variable s, so gain, phase and stability all read from one expression.

### Magnetism & Transformers

- [Electromagnetic Induction](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/electromagnetic-induction/): Faraday and Lenz in working form: why only changing flux makes a voltage, how fast counts more than how much, and why the coil always fights the change.
- [Electromagnets & the Solenoid](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/electromagnetism/): Electromagnets and solenoids: ampere-turns, the field a coil produces, what a ferrite core multiplies, and the saturation limit the formula never mentions.
- [The Hall Effect](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/hall-effect/): The Hall effect explained: a sideways voltage from a field and a current, why it needs a semiconductor, and how Hall sensors measure DC current and position.
- [Magnetic Fields](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/magnetic-field/): Magnetic fields from the compass up: what tesla measures, why the field round a wire circles it and falls as 1/r, and how a return conductor kills it.
- [Magnetic Flux](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/magnetic-flux/): Magnetic flux is field times the area it crosses, measured in webers: how flux differs from flux density, why angle matters, and what volt-seconds really means.
- [Motors & Generators: the Principle](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/motors-generators-intro/): One machine, two directions: how force on a conductor makes a motor, how back-emf sets its current and speed, and why every motor is also a generator.
- [Permeability & Core Materials](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/permeability-core-materials/): Permeability, saturation and core choice: what µr really buys, how a magnetic circuit works, and why a one-millimetre air gap changes everything.
- [How Electricity Reaches Your Home](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/power-distribution/): From generator to socket: why the grid transmits at high voltage, what line loss and voltage drop actually cost, and what every transformer in the chain is for.
- [Transformer Losses & Efficiency](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/transformer-losses/): Copper loss, hysteresis and eddy currents: where a transformer's watts go, why efficiency peaks below full load, and why light loads are wasteful.
- [How Transformers Work](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/transformer-principle/): How a transformer works: shared flux, volts per turn, the turns ratio for voltage and current, magnetising current, and why direct current will not do.
- [Transformer Types (Isolation, Auto, Current)](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/transformer-types/): Isolation, auto and current transformers compared: what each one is for, why an autotransformer does not isolate, and why a CT secondary is never opened.
- [Turns Ratio & Impedance Matching](https://www.electronicsinfoline.com/fundamentals/magnetism-transformers/turns-ratio/): The turns ratio squared is the impedance ratio: how a transformer matches a source to a load, what that matching is worth, and what limits its bandwidth.

### Test, Measurement & Lab Practice

- [Bench Power Supplies](https://www.electronicsinfoline.com/fundamentals/test-measurement/bench-power-supply/): A bench supply sets a ceiling on volts and a ceiling on amps, then holds whichever one the load allows. Reading the mode indicator is the habit.
- [Breadboarding & Prototyping](https://www.electronicsinfoline.com/fundamentals/test-measurement/breadboarding/): What a breadboard strip actually joins, what its contacts and row capacitance cost a working circuit, and where the supply loop stops it telling the truth.
- [Test Lead CAT Safety Ratings](https://www.electronicsinfoline.com/fundamentals/test-measurement/cat-safety-ratings/): A CAT rating states where in an installation an instrument may be used, not how many volts it reads, and why the leads carry a rating of their own.
- [Clamp Meters](https://www.electronicsinfoline.com/fundamentals/test-measurement/clamp-meter/): A clamp meter reads current from the field around a conductor, with nothing cut, unplugged or unsoldered, and what its jaw encloses is what the display shows.
- [Continuity & Diode Test Modes](https://www.electronicsinfoline.com/fundamentals/test-measurement/continuity-diode-test/): Continuity answers whether two points are joined, and the diode range answers what kind of junction sits between them. Both work only with the power off.
- [Function Generators](https://www.electronicsinfoline.com/fundamentals/test-measurement/function-generator/): A function generator makes the signal a circuit is tested with. Its amplitude setting assumes a matched load, and that assumption is where readings go wrong.
- [Testing Components In-Circuit](https://www.electronicsinfoline.com/fundamentals/test-measurement/in-circuit-testing/): What a meter really measures when the part is still soldered down, which in-place readings settle a question, which only bound it, and when to lift a leg.
- [LCR Meters](https://www.electronicsinfoline.com/fundamentals/test-measurement/lcr-meter/): An LCR meter drives a part at a chosen frequency and reads the size and the timing of what comes back, then reports it as a series or a parallel pair.
- [Accuracy, Resolution & Measurement Error](https://www.electronicsinfoline.com/fundamentals/test-measurement/measurement-accuracy/): Resolution is how finely a meter divides, accuracy is how close it gets, and the two are unrelated. A reading is a range, and its width is on the datasheet.
- [Measuring Voltage, Current & Resistance](https://www.electronicsinfoline.com/fundamentals/test-measurement/measuring-v-i-r/): Voltage is measured across a part with the circuit intact, current through a break in the loop, and resistance with the power off and one end lifted clear.
- [Meter Loading Effects](https://www.electronicsinfoline.com/fundamentals/test-measurement/meter-loading/): Every instrument becomes part of the circuit it measures. The error follows one ratio: the meter's own resistance against the resistance it is placed on.
- [Using a Multimeter](https://www.electronicsinfoline.com/fundamentals/test-measurement/multimeter/): What the jacks, the counts and the ranges of a digital multimeter mean, how to take a reading you can trust, and the one wiring error that destroys meters.
- [Using an Oscilloscope](https://www.electronicsinfoline.com/fundamentals/test-measurement/oscilloscope/): An oscilloscope draws voltage against time on a ruled screen. Vertical, timebase and trigger settings decide what you see, and bandwidth decides what you can.
- [Advanced Oscilloscope Measurements](https://www.electronicsinfoline.com/fundamentals/test-measurement/oscilloscope-measurements/): Triggering picks the moment a scope looks. Harmonics and a rise-time budget say how much of a fast edge belongs to the circuit and how much to the instrument.
- [How to Read a Datasheet](https://www.electronicsinfoline.com/fundamentals/test-measurement/reading-datasheets/): How a datasheet's guaranteed limits, typical figures and curves differ, what the conditions cell does to each, and which of its numbers a design may lean on.
- [Oscilloscope Probes & 10x Attenuation](https://www.electronicsinfoline.com/fundamentals/test-measurement/scope-probes/): A 10x probe divides the signal by ten to present a tenth of the capacitance. Compensation makes that division hold at every frequency, and it needs setting.
- [Soldering Basics](https://www.electronicsinfoline.com/fundamentals/test-measurement/soldering-basics/): A solder joint is a metallurgical bond, a thermal system with its own time constant, and a resistance in the load path. What each of those means at the bench.

## School of Components

### Resistors & Resistive Devices

- [Current-Sense (Shunt) Resistors](https://www.electronicsinfoline.com/components/resistors/current-sense-resistor/): A current-sense resistor turns amperes into a small voltage you can read. Sizing one trades signal against heat, and most of its error lives in the wiring.
- [E-Series Preferred Values (E12, E24, E96)](https://www.electronicsinfoline.com/components/resistors/e-series/): Why a catalogue stocks 2.7 and 3.3 with nothing between them: how E12, E24 and E96 cut a decade into logarithmic steps, and what the gaps cost a design.
- [Light-Dependent Resistors (LDR)](https://www.electronicsinfoline.com/components/resistors/ldr/): How a light-dependent resistor turns light into resistance along a power law, what its compressed scale and its slow answer cost a circuit, and how to read it.
- [Potentiometers & Trimmers](https://www.electronicsinfoline.com/components/resistors/potentiometer/): One resistive track and a sliding wiper: how a potentiometer divides a voltage, what taper really does, and how far a load bends the output away.
- [Pull-Up & Pull-Down Resistors](https://www.electronicsinfoline.com/components/resistors/pull-up-pull-down/): Why a logic pin with nothing on it reads neither high nor low, what a pull-up or pull-down resistor does about that, and how to size one from both ends.
- [The Resistor](https://www.electronicsinfoline.com/components/resistors/resistor/): The resistor as a real component: what it does, how to use and size one, how tolerance and temperature move its value, and how professionals select them.
- [Resistor Color Code](https://www.electronicsinfoline.com/components/resistors/resistor-color-code/): How the coloured bands on a resistor spell out a value and a tolerance, which end to start reading from, and why a five-band part is not a four-band one.
- [Resistor Failure Modes](https://www.electronicsinfoline.com/components/resistors/resistor-failure-modes/): Why an overloaded resistor drifts high long before it opens, what a single pulse does that a slow overload does not, and how to tell which one happened.
- [Resistor Power Ratings & Derating](https://www.electronicsinfoline.com/components/resistors/resistor-power-rating/): A resistor's power rating is a temperature limit written in watts. How the derating curve shrinks it in warm air, how hot the body gets, and what pulses change.
- [Choosing the Right Resistor](https://www.electronicsinfoline.com/components/resistors/resistor-selection/): Choosing a resistor settles four things: the value, the power rating where the part sits, the tolerance and the package, worked through on an LED limiter.
- [Resistor Tolerance & Precision](https://www.electronicsinfoline.com/components/resistors/resistor-tolerance/): A marked resistance is a band rather than a number. What a tolerance figure promises, how two of them stack in a divider, and what moves the value later.
- [Resistor Types & Construction](https://www.electronicsinfoline.com/components/resistors/resistor-types/): Carbon composition, thick film, metal film and wirewound: what the element is made of and cut into, and what that settles about drift, noise and speed.
- [RTDs (Resistance Temperature Detectors)](https://www.electronicsinfoline.com/components/resistors/rtd/): A platinum RTD turns temperature into resistance that repeats from part to part. The curve behind the straight line, and what two, three and four wires cost.
- [SMD Package Sizes & Through-Hole](https://www.electronicsinfoline.com/components/resistors/smd-packages/): 0402, 0603, 0805 and 1206: what the four digits measure, the land pattern and dissipation that follow, and how much conductor a package adds.
- [SMD Resistor Codes](https://www.electronicsinfoline.com/components/resistors/smd-resistor-codes/): How the three-digit, four-digit and EIA-96 markings on a chip resistor decode, which of them collide on a reel, and what a printed code never tells you.
- [Strain Gauges](https://www.electronicsinfoline.com/components/resistors/strain-gauge/): A resistor bonded to a surface reports strain as a tenth of a per cent: gauge factor, the bridge that subtracts the rest, and why warming looks like strain.
- [Thermistors (NTC & PTC)](https://www.electronicsinfoline.com/components/resistors/thermistor/): An NTC thermistor's resistance collapses as it warms. The beta model, the straight line hiding in reciprocal-temperature coordinates, and how to read one.
- [Varistors (MOV)](https://www.electronicsinfoline.com/components/resistors/varistor/): A varistor collapses to a low resistance above a set voltage, clamping a surge and turning its energy into heat inside itself, and wearing out as it does.

### Capacitors

- [The Capacitor as a Component](https://www.electronicsinfoline.com/components/capacitors/capacitor-component/): What a capacitor is once it stops being a physics idea and becomes a part you buy: what sets its value, what the catalogue line means, and what it hides.
- [Capacitor Failure Modes & Aging](https://www.electronicsinfoline.com/components/capacitors/capacitor-failure-modes/): Most capacitors wear out rather than break. What drifts, which families fail open and which fail short, and how to catch the wear before the circuit does.
- [Capacitor Markings & Codes](https://www.electronicsinfoline.com/components/capacitors/capacitor-markings/): Reading the codes printed on a capacitor: the three-digit picofarad rule, the letter that carries tolerance, and two polarity marks that mean opposite things.
- [Capacitor Voltage Ratings & Derating](https://www.electronicsinfoline.com/components/capacitors/capacitor-ratings/): A capacitor's voltage rating is an insulation limit, not an operating point. What stacks against it, why series strings share badly, and why AC is different.
- [Choosing the Right Capacitor](https://www.electronicsinfoline.com/components/capacitors/capacitor-selection/): Choosing a capacitor is four questions in a fixed order. One converter output scored three ways, and why the marked value is the last thing that decides it.
- [Testing Capacitors](https://www.electronicsinfoline.com/components/capacitors/capacitor-testing/): Proving a capacitor dead, then proving it good. What capacitance, ESR and leakage each reveal, why the test frequency changes the answer, and what no test sees.
- [Ceramic Capacitors & MLCC Classes](https://www.electronicsinfoline.com/components/capacitors/ceramic-capacitors/): Class 1 and class 2 ceramics are different parts sharing a name. What the three-character code promises, and why class 2 loses most of its value in use.
- [Coupling & DC Blocking Capacitors](https://www.electronicsinfoline.com/components/capacitors/coupling-capacitors/): A coupling capacitor passes the signal and blocks the DC, so two stages hold different operating points. What the corner costs, and where the value comes from.
- [Decoupling & Bypass Capacitors](https://www.electronicsinfoline.com/components/capacitors/decoupling-capacitors/): Decoupling is a loop-inductance problem in a capacitance costume. Why placement beats value, what paralleling buys, and the peak between bulk and local parts.
- [Electrolytic Capacitors](https://www.electronicsinfoline.com/components/capacitors/electrolytic-capacitors/): The aluminium electrolytic buys huge capacitance with a grown oxide and a wet element. Why it is polarised, what wears it out, and how long it really lasts.
- [ESR & Capacitor Parasitics](https://www.electronicsinfoline.com/components/capacitors/esr/): Series resistance and inductance are what stop a capacitor behaving like one. Where they come from, what they cost in heat, and where the part gives up.
- [Film Capacitors](https://www.electronicsinfoline.com/components/capacitors/film-capacitors/): Film capacitors trade size for stability, low loss and a fault that heals itself. What the dielectric choice decides, and where the family earns its volume.
- [Motor Run & Start Capacitors](https://www.electronicsinfoline.com/components/capacitors/motor-capacitors/): A single-phase motor cannot start itself. The capacitor that fixes it, why start and run duties are different, and the charge it holds after the supply is off.
- [X & Y Safety Capacitors](https://www.electronicsinfoline.com/components/capacitors/safety-capacitors/): X and Y capacitors are classified by what a failure must not do. Where each sits, why Y values are tiny, and why an X capacitor always has a resistor by it.
- [Supercapacitors](https://www.electronicsinfoline.com/components/capacitors/supercapacitors/): Supercapacitors sit between a capacitor and a battery: farads at a couple of volts, enormous peak power, and a voltage that never sits still while it works.
- [Tantalum Capacitors](https://www.electronicsinfoline.com/components/capacitors/tantalum-capacitors/): Tantalum packs more charge into a package than anything else, and fails as a short if you let it. Derating, inrush limiting and the polymer alternative.

### Inductors, Electromechanical & Hardware

- [Battery Charging Basics](https://www.electronicsinfoline.com/components/inductors-electromechanical/battery-charging/): Why charging is two phases rather than one, where the time goes, what a higher charge current does and does not buy, and how each chemistry knows to stop.
- [Battery Types & Chemistry Basics](https://www.electronicsinfoline.com/components/inductors-electromechanical/battery-types/): What separates the battery chemistries: discharge curve shape, energy per kilogram, internal resistance, and why runtime is never capacity divided by current.
- [Buzzers & Speakers](https://www.electronicsinfoline.com/components/inductors-electromechanical/buzzers-speakers/): How a coil in a magnetic gap moves air, why cone travel goes as one over frequency squared, where the watt goes, and how a piezo element differs entirely.
- [Common-Mode Chokes](https://www.electronicsinfoline.com/components/inductors-electromechanical/common-mode-choke/): Two windings on one core that block noise travelling the same way along both conductors while letting the signal or the supply current through untouched.
- [Connectors Overview](https://www.electronicsinfoline.com/components/inductors-electromechanical/connectors/): Connectors as components: why contact resistance is really a contact force, what a chain of them costs a supply rail, and why pin ratings do not add up.
- [Crystals & Ceramic Resonators](https://www.electronicsinfoline.com/components/inductors-electromechanical/crystals-resonators/): Quartz crystals and ceramic resonators as components: the four-element model, the two resonances a few parts per million apart, and what the load capacitors do.
- [DC Motors](https://www.electronicsinfoline.com/components/inductors-electromechanical/dc-motor/): Why a DC motor's torque falls linearly with speed, where its maximum power and its best efficiency sit, and why a stalled motor is just its winding resistance.
- [Ferrite Beads](https://www.electronicsinfoline.com/components/inductors-electromechanical/ferrite-beads/): A ferrite bead is a deliberately lossy inductor that turns high-frequency noise into heat, and below its crossover it can resonate and make that noise worse.
- [Fuses & Fuse Selection](https://www.electronicsinfoline.com/components/inductors-electromechanical/fuses/): How a fuse decides when to melt, why its rated current is not its melting current, and what the voltage rating and breaking capacity are really protecting.
- [Heat Sinks & Thermal Basics](https://www.electronicsinfoline.com/components/inductors-electromechanical/heatsinks/): A heatsink is one resistance in a chain from junction to air, and the junction temperature is simply the ambient plus the power multiplied by that chain.
- [The Inductor as a Component](https://www.electronicsinfoline.com/components/inductors-electromechanical/inductor-component/): What an inductor is as a purchasable part: the six numbers on its catalogue line, why the core sets both the turns and the headroom, and how to pick one.
- [Inductor Saturation](https://www.electronicsinfoline.com/components/inductors-electromechanical/inductor-saturation/): What happens when a core runs out of magnetic material: the inductance collapses, the current runs away, and the rating on the datasheet is one of several.
- [Inductor Types & Core Choices](https://www.electronicsinfoline.com/components/inductors-electromechanical/inductor-types/): Core materials and core shapes compared on one geometry: what powdered iron, MnZn ferrite, NiZn ferrite and laminated steel each cost you, and where each stops.
- [Driving Relays Safely](https://www.electronicsinfoline.com/components/inductors-electromechanical/relay-driving/): Driving a relay coil from a logic pin: sizing the base resistor, why the clamp diode goes cathode-to-rail, and the four ways this small circuit is got wrong.
- [Relays](https://www.electronicsinfoline.com/components/inductors-electromechanical/relays/): A relay is a switch worked by an electromagnet: what the coil costs, why it lets go later than it picks up, and why the isolation is the reason to fit one.
- [Resettable (PTC) Fuses](https://www.electronicsinfoline.com/components/inductors-electromechanical/resettable-fuses/): A polymer PTC latches into a high resistance instead of melting, resets when the supply goes, and gives up isolation and speed to do it. Where that trade wins.
- [Steppers & Servos: an Introduction](https://www.electronicsinfoline.com/components/inductors-electromechanical/stepper-servo-intro/): Two ways to make a motor go to a position: a stepper that asserts one and a servo that measures it, and why microstepping buys resolution but not accuracy.
- [Switches & Pushbuttons](https://www.electronicsinfoline.com/components/inductors-electromechanical/switches/): Switches and pushbuttons as components: contact bounce and what it costs, poles and throws, contact resistance, and why opening a switch is the hard part.
- [Transformers as Components](https://www.electronicsinfoline.com/components/inductors-electromechanical/transformer-component/): Buying a transformer: what the VA rating really measures, why the secondary voltage is two numbers, and what happens in the first few cycles after switch-on.
- [Wire, Cable & Gauge Selection](https://www.electronicsinfoline.com/components/inductors-electromechanical/wire-and-cable/): Choosing wire by voltage drop rather than by guesswork: the gauge ladder, why the conductor is twice the run, and why current rating is a code question.

### Diodes & Rectification

- [Diode Clippers & Clampers](https://www.electronicsinfoline.com/components/diodes/clippers-clampers/): A clipper removes part of a waveform; a clamper moves the whole of it. Two circuits with the same parts in different places, and how to tell them apart.
- [The Diode](https://www.electronicsinfoline.com/components/diodes/diode/): A diode passes current one way and blocks it the other, and charges a small voltage for the privilege. The band, the drop, and the four ratings that decide one.
- [Diode I-V Characteristics](https://www.electronicsinfoline.com/components/diodes/diode-iv-curve/): A diode has no switch-on voltage. It has an exponential curve, and 0.7 V is only where that curve crosses the current you happened to be using.
- [Diode Models (Ideal to Exponential)](https://www.electronicsinfoline.com/components/diodes/diode-models/): Ideal, constant drop, constant drop plus slope, or the full exponential. Which simplification of a diode to use, and how wrong each one is on a real circuit.
- [Testing Diodes](https://www.electronicsinfoline.com/components/diodes/diode-testing/): Try it both ways round. What a meter's diode range actually measures, what each pattern of reading means, and why the ohms range answers the wrong question.
- [Flyback (Freewheeling) Diodes](https://www.electronicsinfoline.com/components/diodes/flyback-diode/): An inductor's current cannot stop, so opening a switch demands enormous voltage. A diode across the coil gives it a loop, and the clamp sets the release time.
- [Full-Wave & Bridge Rectifiers](https://www.electronicsinfoline.com/components/diodes/full-wave-rectifier/): Four diodes in a bridge, or two on a centre-tapped winding, use both halves of every cycle. What each topology costs in drops, in diodes and in winding.
- [Half-Wave Rectifiers](https://www.electronicsinfoline.com/components/diodes/half-wave-rectifier/): One diode turns alternating current into something that only flows one way, at the cost of half the cycle. What comes out, and what the diode has to hold off.
- [IR LEDs & Photointerrupters](https://www.electronicsinfoline.com/components/diodes/ir-optics/): An infrared emitter and detector twenty millimetres apart, with the room's light twice as bright as the signal. Why the beam is modulated, and what sets range.
- [LEDs](https://www.electronicsinfoline.com/components/diodes/led/): An LED's colour is fixed by its material, and that colour sets a floor under its forward voltage. Why current, not voltage, is the thing you control.
- [LED Current Limiting & Drive Circuits](https://www.electronicsinfoline.com/components/diodes/led-circuits/): A resistor is the usual way to set an LED's current, and headroom is what makes it work. Series strings, why parallel needs care, and when to use a driver.
- [Photodiodes](https://www.electronicsinfoline.com/components/diodes/photodiode/): A reverse-biased junction turns light into current in exact proportion over six decades. How responsivity works, the two modes, and where the floor is.
- [The PN Junction](https://www.electronicsinfoline.com/components/diodes/pn-junction/): Two doped regions meet, carriers cross, and a barrier builds itself from what they leave behind. What the depletion region is, and what bias does to it.
- [Schottky Diodes](https://www.electronicsinfoline.com/components/diodes/schottky-diode/): A metal-to-silicon junction drops about half as much as a PN one and stores no charge, so it switches instantly. The price is leakage and a low voltage ceiling.
- [Seven-Segment Displays](https://www.electronicsinfoline.com/components/diodes/seven-segment-display/): Ten digits from seven bars, each bar an LED. Common anode or cathode, one resistor per segment, and why multiplexing trades pins for peak current.
- [Smoothing Capacitors & Ripple](https://www.electronicsinfoline.com/components/diodes/smoothing-ripple/): A reservoir capacitor turns a rectifier's humps into a rail with a sawtooth on it. What sets the ripple, and what it does to the diode current.
- [TVS Diodes & Transient Protection](https://www.electronicsinfoline.com/components/diodes/tvs-diode/): A transient suppressor sits idle for years and clamps in nanoseconds. How the five voltages line up, why energy is the rating, and what its capacitance costs.
- [Voltage Multipliers](https://www.electronicsinfoline.com/components/diodes/voltage-multipliers/): Diodes and capacitors stacked in stages turn a modest AC source into a high DC voltage. Each stage adds two peaks, and each stage costs regulation and ripple.
- [Zener Diodes](https://www.electronicsinfoline.com/components/diodes/zener-diode/): A Zener diode breaks down backwards at a designed voltage without damage, holding roughly that voltage as its current varies. What it is good for, and what not.
- [Zener Voltage Regulators](https://www.electronicsinfoline.com/components/diodes/zener-regulator/): A resistor and a Zener hold a rail steady by wasting whatever the load leaves. How to size both, the two worst corners, and where the arrangement runs out.

### Transistors

- [Bias Stability & Thermal Runaway](https://www.electronicsinfoline.com/components/transistors/bias-stability/): A bias point that depends on the device's gain or on its own temperature will move, and one loop gain decides whether it settles somewhere or runs away.
- [The Bipolar Junction Transistor (BJT)](https://www.electronicsinfoline.com/components/transistors/bjt/): A bipolar junction transistor is three doped layers with a very thin one in the middle, and that thinness is what turns a small base current into a large one.
- [The BJT as a Switch](https://www.electronicsinfoline.com/components/transistors/bjt-as-switch/): Driving a transistor into saturation makes it a switch, and the design rule is to supply far more base current than the worst device would need.
- [BJT Biasing](https://www.electronicsinfoline.com/components/transistors/bjt-biasing/): Biasing sets a transistor's operating point so that it survives the spread in current gain, and a divider with an emitter resistor is how that is done.
- [How a BJT Works](https://www.electronicsinfoline.com/components/transistors/bjt-operation/): A BJT's collector current is set by the base-emitter voltage on an exponential, and the base current is only what fails to make the crossing.
- [BJT Operating Regions](https://www.electronicsinfoline.com/components/transistors/bjt-regions/): Cut-off, active and saturation are three places one transistor can sit, and which one it lands in is decided by the load rather than by the device.
- [Common-Collector & Common-Base Stages](https://www.electronicsinfoline.com/components/transistors/common-collector-base/): The emitter follower buys current gain and a low output resistance with no voltage gain; the common-base stage buys bandwidth with no current gain.
- [Common-Emitter Amplifiers](https://www.electronicsinfoline.com/components/transistors/common-emitter/): A common-emitter stage turns a small input voltage into a large inverted output, and its gain is transconductance multiplied by whatever the collector drives.
- [Current Mirrors](https://www.electronicsinfoline.com/components/transistors/current-mirror/): A current mirror copies one current into another branch by giving two matched transistors the same base-emitter voltage, and mismatch is its real limit.
- [Darlington Pairs](https://www.electronicsinfoline.com/components/transistors/darlington-pair/): Feeding one transistor's emitter into another's base multiplies their gains, at the cost of two junction drops in and a much worse saturation out.
- [The Differential Pair](https://www.electronicsinfoline.com/components/transistors/differential-pair/): Two transistors sharing one tail current amplify the difference between their two inputs and largely ignore whatever both inputs happen to do together.
- [The H-Bridge](https://www.electronicsinfoline.com/components/transistors/h-bridge/): Four switches in two legs let one supply drive a motor either way, and the whole art of the arrangement is never turning both switches in a leg on at once.
- [IGBTs](https://www.electronicsinfoline.com/components/transistors/igbt/): An IGBT takes a MOSFET's insulated gate and uses it to drive a bipolar output, giving a low fixed on-state voltage at the cost of a slow turn-off.
- [JFETs](https://www.electronicsinfoline.com/components/transistors/jfet/): A JFET conducts with no gate drive and is turned off by a reverse-biased gate, so it takes almost no input current and gives up transconductance in return.
- [Load Line Analysis](https://www.electronicsinfoline.com/components/transistors/load-line/): A load line is the straight line a supply and a resistor draw on a device's own axes, and where it crosses the device's curve is the circuit's answer.
- [MOSFETs](https://www.electronicsinfoline.com/components/transistors/mosfet/): A MOSFET gate is separated from the channel by an insulator, so it draws no steady current, and when it conducts the device behaves as a resistance.
- [The MOSFET as a Switch](https://www.electronicsinfoline.com/components/transistors/mosfet-as-switch/): A MOSFET used as a switch is a resistor you can turn off, and nearly everything that matters about it follows from how hard you drive the gate.
- [MOSFET Gate Drive & Switching Losses](https://www.electronicsinfoline.com/components/transistors/mosfet-gate-drive/): A MOSFET gate takes charge rather than voltage, and how quickly you deliver that charge decides how much the switching itself ends up costing in watts.
- [How MOSFETs Work](https://www.electronicsinfoline.com/components/transistors/mosfet-operation/): Above its threshold a MOSFET's gate creates a channel, and the drain current follows the square of the overdrive rather than an exponential.
- [Choosing Between MOSFET & BJT](https://www.electronicsinfoline.com/components/transistors/mosfet-vs-bjt/): Choosing between a MOSFET and a bipolar transistor comes down to five questions, and each of them has a number attached that settles the argument.
- [Phototransistors & Optocouplers](https://www.electronicsinfoline.com/components/transistors/phototransistor-optocoupler/): A phototransistor turns light into current with gain, and an optocoupler pairs one with an LED so a signal can cross a gap nothing electrical crosses.
- [Push-Pull & Class AB Output Stages](https://www.electronicsinfoline.com/components/transistors/push-pull-output/): Two complementary devices, one pushing and one pulling, drive a load efficiently — provided a small bias closes the gap between them and tracks their heat.
- [Small-Signal Models: an Introduction](https://www.electronicsinfoline.com/components/transistors/small-signal-model/): A small-signal model replaces a transistor with three linear elements that describe how it behaves for tiny changes about one operating point.
- [Transistor Gain (β / hFE)](https://www.electronicsinfoline.com/components/transistors/transistor-gain/): Current gain is a band rather than a value, it moves with current and temperature, and good design arranges not to depend on which device you fitted.
- [Transistor Oscillators](https://www.electronicsinfoline.com/components/transistors/transistor-oscillators/): An oscillator is an amplifier fed back on itself, and it settles on the one frequency where the loop has enough gain and no phase shift left over.
- [Transistor Packages & Thermal Design](https://www.electronicsinfoline.com/components/transistors/transistor-packages-thermal/): Choosing a transistor package is a thermal decision before it is a mechanical one, and the arithmetic that settles it takes one subtraction and one division.
- [Testing Transistors](https://www.electronicsinfoline.com/components/transistors/transistor-testing/): A multimeter can tell you a transistor's type, its pinout and whether it has failed — and it can also mislead you, in four ways worth knowing about.

### Thyristors & Power Devices

- [Crowbar Overvoltage Protection](https://www.electronicsinfoline.com/components/power-devices/crowbar-circuit/): A protection circuit that shorts the supply on purpose: what it saves, why it needs a fuse to work with, and why response time matters more than the trip point.
- [AC Phase Control & Dimmers](https://www.electronicsinfoline.com/components/power-devices/phase-control/): How a dimmer controls power by choosing when in each half cycle to start, why the knob does not track the brightness, and why the whole circuit is live.
- [Snubbers & Power Device Protection](https://www.electronicsinfoline.com/components/power-devices/power-device-protection/): Why interrupting current makes a voltage the circuit never had, what a snubber changes, what a clamp changes instead, and why neither of them is free.
- [Thyristors (SCR)](https://www.electronicsinfoline.com/components/power-devices/scr/): A thyristor is a switch you can only turn on: what the gate does in its first microsecond, why it stops mattering after that, and how you ever get it off again.
- [Solid-State Relays](https://www.electronicsinfoline.com/components/power-devices/solid-state-relay/): A relay with no moving parts: what crosses the isolation barrier, why zero-cross switching costs you resolution, and the current above which no heatsink helps.
- [TRIACs & DIACs](https://www.electronicsinfoline.com/components/power-devices/triac-diac/): A triac is a thyristor that works both ways round, and a diac is the part that tells it when: what each one does, and what an inductive load does to both.

### Essential Integrated Circuits

- [555 Astable Circuits](https://www.electronicsinfoline.com/components/essential-ics/555-astable/): A timer with its own capacitor to charge and discharge runs forever: the two intervals, the duty cycle it cannot get below, and what actually sets the rate.
- [555 Monostable & Timing Circuits](https://www.electronicsinfoline.com/components/essential-ics/555-monostable/): One dip on the trigger gives one pulse of a length you picked: where the logarithm of three comes from, why datasheets write 1.1, and what sets the ceiling.
- [Active Filters](https://www.electronicsinfoline.com/components/essential-ics/active-filters/): Filters with an amplifier inside: sharper corners without inductors, stages that ignore each other, and a Q set by two resistors nobody thinks about.
- [ADCs & DACs: an Introduction](https://www.electronicsinfoline.com/components/essential-ics/adc-dac-intro/): What a converter actually gives up on each of its two axes: the levels it cannot tell apart, the moments it does not look, and which limit binds when.
- [Audio Amplifier ICs](https://www.electronicsinfoline.com/components/essential-ics/audio-amplifier-ics/): What an audio power IC leaves you to decide: two resistors for the gain, one capacitor for the bass, and a supply rail that sets the power first.
- [Comparators & Hysteresis](https://www.electronicsinfoline.com/components/essential-ics/comparator/): A circuit whose only answer is which input is higher, why that answer chatters when the signal is noisy, and how positive feedback makes it decide once.
- [IC Packages & Pin Numbering](https://www.electronicsinfoline.com/components/essential-ics/ic-packages/): How IC pin numbering works and why it never changes with the package, what shrinking a footprint costs in heat, and what the pitch decides about assembly.
- [Powering ICs Correctly](https://www.electronicsinfoline.com/components/essential-ics/ic-power-decoupling/): Where a decoupling capacitor has to physically go, why the enclosed loop area is the design variable, and what vias and a split plane do to it.
- [Instrumentation Amplifiers](https://www.electronicsinfoline.com/components/essential-ics/instrumentation-amplifier/): Three op-amps, one gain resistor, and inputs that touch nothing: how a bridge signal of two millivolts survives riding on two volts of common level.
- [What Is an Integrated Circuit?](https://www.electronicsinfoline.com/components/essential-ics/integrated-circuit/): Why a circuit built all at once in one piece of silicon is cheap, matched and reliable, and what that costs in area, heat and the parts that will not fit.
- [The Inverting Amplifier](https://www.electronicsinfoline.com/components/essential-ics/inverting-amplifier/): The commonest op-amp circuit: how a virtual ground makes the gain a ratio of two resistors, and why the source driving it is part of that ratio.
- [Linear Voltage Regulators (78xx & LDO)](https://www.electronicsinfoline.com/components/essential-ics/linear-regulators/): How a linear regulator holds an output steady by adjusting a series element, what dropout really costs, and why its efficiency is set by the supply.
- [Logic Families (TTL & CMOS)](https://www.electronicsinfoline.com/components/essential-ics/logic-families/): What separates one logic family from another: standing current against switching current, what an input costs a driver, and which limit decides fan-out.
- [Logic Levels & Digital Signals](https://www.electronicsinfoline.com/components/essential-ics/logic-levels/): What the four threshold voltages on a logic datasheet mean, why the gaps between them are the noise margin, and what happens when two rails have to talk.
- [Motor Driver ICs](https://www.electronicsinfoline.com/components/essential-ics/motor-driver-ics/): What a motor driver IC adds beyond four switches: a lockout you cannot defeat, a current limit, a thermal cut-out, and a real rating set by its package.
- [The Non-Inverting Amplifier & Voltage Follower](https://www.electronicsinfoline.com/components/essential-ics/non-inverting-amplifier/): Gain set by a divider on the output, an input that draws almost nothing, and the follower: the least glamorous op-amp circuit and the most accurate one.
- [The Operational Amplifier](https://www.electronicsinfoline.com/components/essential-ics/op-amp/): What an operational amplifier is, why its enormous gain makes it useless on its own, and the three-element model that explains everything it does next.
- [Op-Amp Golden Rules & Negative Feedback](https://www.electronicsinfoline.com/components/essential-ics/op-amp-golden-rules/): Negative feedback, the two rules that come out of it, and the arithmetic showing why an amplifier's own gain stops deciding what its circuit does.
- [Op-Amp Integrators & Differentiators](https://www.electronicsinfoline.com/components/essential-ics/op-amp-integrator-differentiator/): Swap a resistor for a capacitor and the inverting amplifier starts totalling or reporting slope, and both textbook circuits need a fix before they work.
- [Real Op-Amp Limitations](https://www.electronicsinfoline.com/components/essential-ics/op-amp-limitations/): Gain that falls with frequency, an output with a speed limit, and errors that arrive with no signal at all: the reasons a real op-amp is not the ideal one.
- [PWM Generation with the 555](https://www.electronicsinfoline.com/components/essential-ics/pwm-with-555/): How driving a 555's control pin turns an astable into a pulse-width modulator, what that does to the duty ratio, and why the frequency moves with it.
- [Reading IC Datasheets](https://www.electronicsinfoline.com/components/essential-ics/reading-ic-datasheets/): Which sections of an IC datasheet actually bind, how to read a timing diagram into a clock ceiling, and what a temperature grade and an ordering code decide.
- [Linear Regulator Thermal Design](https://www.electronicsinfoline.com/components/essential-ics/regulator-thermal-design/): How to turn a linear regulator's dissipation into a junction temperature, size the heatsink it needs, and notice when a smaller supply would do the job instead.
- [Summing & Difference Amplifiers](https://www.electronicsinfoline.com/components/essential-ics/summing-difference-amps/): Adding several signals at one node that does not move, subtracting two at a matched pair of dividers, and why the second one is so much harder than it looks.
- [Switching Regulators: an Introduction](https://www.electronicsinfoline.com/components/essential-ics/switching-regulator-intro/): Why a switch that is never half on wastes almost nothing, how a buck converter's duty ratio sets its output, and where the remaining losses come from.
- [The 555 Timer](https://www.electronicsinfoline.com/components/essential-ics/timer-555/): A divider, two comparators and a latch in one package, and why its timing does not care what supply voltage you give it or how that voltage drifts.
- [Voltage References](https://www.electronicsinfoline.com/components/essential-ics/voltage-references/): What separates a voltage reference from a regulator, why its temperature coefficient usually dominates the error budget, and when a better one stops helping.
- [Op-Amp Oscillators (Wien Bridge)](https://www.electronicsinfoline.com/components/essential-ics/wien-bridge-oscillator/): How an RC network picks one frequency, why the amplifier's gain has to be exactly three, and what has to adjust that gain continuously for the circuit to work.

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- [RF circuits](https://www.electronicsinfoline.com/rf-circuits): FM transmitter and the RF lessons behind it
- [Antennas](https://www.electronicsinfoline.com/antennas): DIY 2.4 GHz antennas sized from the wavelength
- [PCB design](https://www.electronicsinfoline.com/pcb-design): PCB layout rules with the formulas
- [Resources](https://www.electronicsinfoline.com/resources): guides for choosing tools and parts
- [Circuit simulators compared](https://www.electronicsinfoline.com/resources/circuit-simulators): nine simulators tested in September 2026
- [Buying electronic components in India](https://www.electronicsinfoline.com/resources/buy-electronic-components-india): ten shops compared, customs duty and IGST on imports
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- [About](https://www.electronicsinfoline.com/about): history since 18 October 2000