Operational Amplifier - Internal Circuitry of 741 Type Op-amp

Internal Circuitry of 741 Type Op-amp

Though designs vary between products and manufacturers, all op-amps have basically the same internal structure, which consists of three stages:

1. Differential amplifier — provides low noise amplification, high input impedance, usually a differential output.
2. Voltage amplifier — provides high voltage gain, a single-pole frequency roll-off, usually single-ended output.
3. Output amplifier — provides high current driving capability, low output impedance, current limiting and short circuit protection circuitry.

IC op-amps as implemented in practice are moderately complex integrated circuits. A typical example is the ubiquitous 741 op-amp designed by Dave Fullagar in Fairchild Semiconductor after the remarkable Widlar LM301. Thus the basic architecture of the 741 is identical to that of the 301.