Opamp

An op-amp (operational amplifier) is a high-gain differential amplifier designed to amplify the difference between its two input terminals. It is typically implemented as an integrated circuit and used with feedback to perform various analog signal processing tasks. The two inputs are called non-inverting (+) and inverting (-); the output is a single-ended voltage.

In normal operation, negative feedback sets the closed-loop gain according to external feedback networks. In the ideal model, Aol is infinite, input impedance is infinite, and output impedance is zero, and the voltages at inputs are equal (virtual short). Real devices have finite Aol, finite Zin, finite Zo, input bias currents, input offset voltage.

Important parameters include open-loop gain, gain-bandwidth product (GBP), slew rate, input bias current, input offset voltage, common-mode rejection ratio (CMRR), power supply voltages, input impedance, and output impedance. Typical op-amps have GBP that limits achievable closed-loop bandwidth; higher gain generally reduces bandwidth, and the slew rate limits how fast the output can change.

Common configurations encompass inverting amplifier, non-inverting amplifier, differential amplifier, summing amplifier, and buffer (voltage follower). They are used in amplifiers, active filters, oscillators, comparators, integrators, analog computation, and ADC front ends. Op-amps can operate with single or dual supplies and are chosen to suit voltage ranges and headroom requirements.

History and context: the concept emerged in the mid-20th century; standard general-purpose ICs like the 741 defined the modern op-amp. Today, op-amps are widely available in many technology nodes and come in specialized variants such as rail-to-rail, low-noise, high-speed, or low-power types.