The IC Op-amp comes so close to ideal performance that it is useful to state the characteristics of an ideal amplifier without regard to what is inside the package.
An ideal op-amp would exhibit the following electrical characteristics:
- Infinite voltage gain A.
- Infinite input resistance Rin so that almost any signal source can drive it and there is no loading of the preceding stage.
- Zero output resistance Rout so that output can drive an infinite number of other devices.
- Zero output voltage when input voltage is zero.
- Infinite bandwidth so that any frequency signal from 0 to ∞ Hz can be amplified without attenuation.
- Infinite common-mode rejection ratio so that the output common-mode noise voltage is zero.
- Infinite slew rate so that output voltage changes occur simultaneously with input voltage changes.
There are practical op-amps that can be made to approximate some of these characteristics using a negative feedback arrangement. In particular, the input resistance, output resistance, and bandwidth can be brought close to ideal values by this method.
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