The system will test an individual's blood alcohol level by analyzing the breath exhaled into system, in which the sytem will decide whether to let the individual start the car.
http://www.ee.washington.edu/conselec/Sp96/projects/jeddk2/final/ee498h.htm
transformer balanced input and output with amplifier in between.
http://www.opamplabs.com/425brln.htm
If you need more sensitivity than the 5mhz circuit this circuit provides about ten times more gain. It too is designed around an inexpensive plastic optical fiber detector.
http://www.discovercircuits.com/PDF-FILES/2mhzrvr1.pdf
This circuit is a simple broad band light detector that uses a very inexpensive IC and a PIN photodiode
http://www.discovercircuits.com/PDF-FILES/5mhzfbvr.pdf
A tutorial demonstrating emitter degeneration and shunt feedback techniques.
http://www.electronics-tutorials.com/amplifiers/broad-band-amplifiers.htm
circuit attaches a plastic fiber optic PIN photodiode assembly to a small box containing a small 3v battery and a standard standard BNC plug designed to be plugged into to the input of an oscilloscope with a 50 ohm termination resistor, can detect light p
http://www.imagineeringezine.com/PDF-FILES/50mrvr1.pdf
designed around an inexpensive plastic optical fiber detector and provides quite much gain
http://www.imagineeringezine.com/PDF-FILES/2mhzrvr1.pdf
simple broad band light detector that uses a very inexpensive IC and a PIN photodiode that is packaged for use with plastic optical fibers, bandwidth from 1KHz to over 5MHz
http://www.imagineeringezine.com/PDF-FILES/5mhzfbvr.pdf
The circuit has frequency response ranging from 100Hz to 3MHz; gain is about 30dB.
http://www.uoguelph.ca/~antoon/circ/broadcast.html
switching regulator provides the charge-voltage setpoint with current regulation, and second switching regulator provides 5V system power.
http://www.edn.com/archives/1997/052297/11di_04.htm