Ideal Parameters Revisited
Parameter Description Ideal Value
BW Bandwidth Infinite
A Open Loop Voltage Gain Infinite
ZIN Input Impedance Infinite
ZOUT Output Impedance 0
VOS Input Offset Voltage 0
IB Input Bias Current 0

The ideal op-amp does not draw any input bias current, i.e., the signal current into inverting terminal and non-inverting terminal are both zero. In other words, the input impedance of an ideal op-amp is infinite.

The output terminal acts as an ideal voltage source, i.e., the voltage between the output terminal and ground will always be equal to A (VIN+ - VIN-) and will be independent of the current that may be drawn from the output terminal into a load impedance. In other words, the output impedance of an ideal op-amp ideally is zero.

On the other hand, practical (non-ideal) op-amps draw input bias current (bipolar input stage), have finite input impedance, non-zero output impedance, and offset voltage, as well as finite voltage gain.

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