Operational Amplifiers 101

An operational amplifier or op amp is an electronic circuit that can perform a myriad of functions from amplification to integration. The characteristics of an ideal op amp are: infinite input impedance, infinite open-loop gain, zero output impedance, infinite bandwidth, and zero noise. The device has positive and negative inputs, which when connected to the output can be used to create circuits with positive or negative feedback. Op amps can be used to make amplifiers, comparators, log amps, filters, oscillators, data converters, level translators, references, and more. They can also be used to perform mathematical functions like addition, subtraction, multiplication, and integration. Practical, real-world op amps have finite characteristics, but are close enough to the ideal to develop a wide range of inexpensive, high-performance analog circuits. To serve the varying needs of applications, op amps are built on many different processes including bipolar, CMOS, biCMOS, complementary-bipolar (CB), and gallium arsenide (GaAs).