There may be differences depending on how the amp is fed: whether symmetrically or asymmetrically. These two main concepts are commonly called split supply and single supply, respectively.
http://home.eunet.cz/rysanek/opamp_en.html
http://margo.student.utwente.nl/el/analog/disc-oa.gif
It is not at all difficult to make an op-amp using transistors. This page shows you how and discusses how they work.
http://www.4qdtec.com/opamp.html
This is normal superheterodyne radio receiver. It does not use any coils. It uses a filter and oscillator made by OP-AMP. Converter is also constructed by a OP-AMP detector.
http://www.intio.or.jp/jf10zl/opraio.htm
A band pass filter passes a range of frequencies while rejecting frequencies outside the upper and lower limits of the passband. The range of frequencies to be passed is called the passband and extends from a point below the center frequency to a point ab
http://ourworld.compuserve.com/homepages/Bill_Bowden/opamp.htm#bandpass.gif
The LM12 is a power op amp capable of driving ±25V at ±10A while operating from ±30V supplies.
http://www.national.com/pf/LM/LM12CL.html