Operational amplifier

An operational amplifier is a high-gain differential voltage amplifier, usually used with feedback to set precise gain and perform signal-processing functions in analog circuits.

Negative feedback: A feedback process in which a system's output opposes changes in its input. It stabilizes gain and makes an op amp's behavior depend on external components.
Differential amplifier: An amplifier that responds to the voltage difference between two inputs. An op amp is a highly amplified differential stage with additional internal circuitry.
Inverting amplifier: An op-amp circuit whose output is an amplified, polarity-reversed version of its input. A resistor ratio sets its gain while negative feedback holds the input node near virtual ground.
Comparator: A circuit that compares two input voltages and switches its output according to which is larger. Unlike a linear op-amp circuit, a comparator is designed to switch between output states.
Virtual ground: A circuit node held near ground voltage by feedback despite lacking a direct ground connection. The inverting input often behaves this way when the noninverting input is grounded.
Voltage divider: A circuit of series impedances that produces a fraction of an applied voltage. Feedback networks use dividers to return a controlled portion of output to an input.
Non-inverting amplifier: An op-amp circuit that amplifies an input without reversing its polarity. Its feedback divider sets voltage gain while preserving the input signal's phase.
Operational transconductance amplifier: An amplifier whose output current is controlled by the differential voltage at its inputs. It offers current output rather than the voltage output characteristic of conventional op amps.
Open-loop gain: An amplifier's gain without feedback applied from output to input. Its large value explains why tiny input differences can drive an op amp toward saturation.
Impedance: The frequency-dependent opposition that a circuit presents to alternating current. Input and output impedances shape how op amps interact with surrounding circuits.

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