OUTPUT IMPEDENCE

An ideal op-amp has zero output impedance. This means that the output voltage is independent of output current. Thus an ideal op-amp can act as a perfect internal voltage source with zero internal resistance, so that maximum current can be driven to the load.

Practically, the output impedance of the op-amp is affected by the negative feedback and is given by,

Zout = Zo / (1 + AOL β)

Where,

Zo is the output impedance of op-amp without feedback

AOL is the open-loop gain

β is the feedback factor

Load impedances connected at the output of the op-amp must be much larger than the circuit output impedance, to avoid any significant loss of output as a voltage drop across Zout.