The operational amplifier is a DC amplifier with a large negative gain factor, very high input resistance and very high output resistance. The operational amplifier always operates on the principle of negative feedback based on impedance (mostly involving a resistor or capacitor) whereby connecting various impedances results in a different kind of transfer function, including those associated with an amplifier, totaliser, differentiator, ramp generator, limiter and the like. Operational amplifiers are configured, installed and coordinated on an individual basis.
Fluidlexikon