Engineering

Op-Amp Gain Calculator

Calculate inverting and non-inverting op-amp gain from resistor values. Get gain in V/V, gain in dB, output voltage estimate, input resistor suggestion, and feedback resistor suggestion.

op-amp-gain
Voltage gain
—
Gain in dB—
Output voltage estimate—
Polarity / phase—
Formula used—

Op-amp gain formulas

Two of the most common op-amp gain configurations are the non-inverting amplifier and the inverting amplifier. The non-inverting circuit keeps the output in phase with the input, while the inverting circuit produces a 180-degree phase inversion.

Non-inverting amplifier: Av = 1 + (Rf ÷ Rg) Inverting amplifier: Av = −Rf ÷ Rin Gain in dB: dB = 20 × log10(|Av|)

Worked examples

Non-inverting example: Rf = 10 kΩ, Rg = 1 kΩ Av = 1 + 10,000 ÷ 1,000 = 11 V/V Gain = 20.83 dB Inverting example: Rf = 10 kΩ, Rin = 1 kΩ Av = −10,000 ÷ 1,000 = −10 V/V Gain = 20 dB

Design checks that matter

The resistor ratio sets the ideal closed-loop gain, but the real circuit is also limited by supply rails, output swing, input common-mode range, bandwidth, slew rate, input bias current, noise, and stability. For high gain or high frequency, always verify the selected op amp's gain-bandwidth product and datasheet recommendations.

Trusted references

For deeper op-amp theory, use non-competitor references such as Analog Devices – Non-Inverting Op Amp, Analog Devices – Inverting Op Amp, and Analog Devices – Noise Gain vs. Signal Gain.

Common questions

  • Use Av = 1 + Rf/Rg. Rf is the feedback resistor from output to the inverting input, and Rg is the resistor from the inverting input to ground or reference.
  • Use Av = −Rf/Rin. The negative sign means the output is inverted, or 180 degrees out of phase with the input.
  • Voltage gain in dB is 20 × log10 of the absolute voltage gain. For example, a gain of 10 V/V is 20 dB.
  • The standard non-inverting configuration has Av = 1 + Rf/Rg, so it cannot produce a gain lower than unity without a different circuit topology.
  • Yes. The resistor ratio sets gain, but absolute resistor values affect noise, bias-current errors, current draw, and sometimes stability.
  • No. It calculates ideal resistor-set gain only. For real circuits, check gain-bandwidth product, slew rate, input range, and output swing in the op-amp datasheet.
  • Signal gain depends on the input configuration. Noise gain is the gain seen by the op amp input error sources and is especially important for stability analysis.
  • Only if the output voltage stays within the op amp supply and output-swing limits. Real op amps cannot swing infinitely beyond their supply rails.