Equivalent Circuit of Practical Op Amp

Equivalent Circuit of Practical Op Amp – The  circuit  which represents op-amp parameters in terms of physical components, for the analysis purpose is called equivalent circuit of an op-amp. The equivalent circuit of an op-amp is shown in the Fig. (A)

Equivalent Circuit of Practical Op Amp

The circuit shows the op-amp parameters like input resistance, output resistance, the open loop voltage gain in terms of circuit components like Rin R0 etc. The op-amp amplifies the  difference between the two input

Ideal Voltage Transfer Curve

The output voltage is directly proportional to the difference voltage Vd.

It is to be noted that the op-amp amplifies difference voltage and not the individual input voltages. Thus the output polarity gets decided by the polarity of the difference voltage Vd .

The voltage source AOL, Vd is the Thevenin’s equivalent voltage source while R0 is the Thevenin s equivalent resistance looking back into the output terminals.

The equivalent circuit plays an important role in analysing various op-amp applications as well as in studying the effects of feedback on the performance of op-amp.