Op-Amp Gain Calculator

An op-amp's gain is set by the ratio of its feedback and input resistors.

How the Math Works

The Op-Amp Gain Calculator uses two fundamental formulas based on operational amplifier configurations. For non-inverting amplifiers, the gain is calculated as 1 + (Rf/Rin), where Rf is the feedback resistor and Rin is the input resistor. This formula arises because the non-inverting input maintains a virtual ground, creating a voltage divider network. For inverting amplifiers, the gain is simply -Rf/Rin, where the negative sign indicates phase inversion. Both formulas rely on the principle that the op-amp adjusts its output to make the voltage difference between its inputs effectively zero.

Practical Applications

To use this calculator practically, first identify whether your op-amp circuit is inverting or non-inverting based on the input connection. For non-inverting circuits, measure or select your feedback resistor (Rf) and input resistor (Rin) values, then apply the 1 + Rf/Rin formula to determine the amplification factor. For inverting circuits, use the -Rf/Rin formula instead. Engineers use these calculations when designing audio preamplifiers, signal conditioners, and filter circuits, entering resistor values to predict whether the circuit will meet their amplification requirements before building the physical circuit.

Day-to-Day Use

Understanding op-amp gain calculations helps explain many everyday electronic devices that improve our daily lives. Your smartphone's microphone preamplifier uses non-inverting op-amps to boost your voice during calls, while noise-canceling headphones employ both inverting and non-inverting configurations to process audio signals. Camera flash circuits use inverting amplifiers to control charging currents, and fitness trackers utilize these circuits to amplify the tiny electrical signals from heart rate sensors. Even the simple USB charger in your wall outlet contains op-amps that regulate voltage output, ensuring your devices charge safely and efficiently.

Worked example

Rf 10k, Rin 1k non-inverting gives a gain of 11.

FAQ