Q.Draw the ac equivalent circuit of op-amp.

An operational amplifier (op-amp) is a compact integrated circuit that behaves as a direct-coupled, very high-gain differential amplifier. Its name comes from its early use in analog computers, where it carried out mathematical operations such as addition, subtraction, integration and differentiation.

Internally an op-amp is a chain of stages: a differential input stage that responds to the difference of its two inputs, a high-gain intermediate stage, a level-shifting (DC) stage and a low-impedance output stage. Externally it presents just a few terminals — an inverting input $(-)$, a non-inverting input $(+)$, the output, and dual supply pins $+V_{CC}$ and $-V_{EE}$. Its schematic symbol is a triangle pointing toward the output, with the two inputs on the left face.

Because its open-loop gain is enormous, the circuit's behaviour is fixed almost entirely by external resistors and capacitors that provide feedback, making the op-amp a universal building block. Its uses fall into two families: linear applications (inverting and non-inverting amplifiers, adders, subtractors, integrators, filters) where feedback keeps operation in the active region, and non-linear applications (comparators, Schmitt triggers, log/anti-log amplifiers) where the device saturates or exploits a device curve. Op-amp ICs such as the 741 are supplied in standard packages — the metal can (TO-5/TO-99), the dual-in-line package (DIP) and the flat pack — which protect the silicon die and bring its terminals out as pins.