Op-Amp Gain Calculator
Calculate voltage gain, gain in dB and output voltage for inverting and non-inverting op-amp configurations.
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What this tool does
Calculate voltage gain, gain in dB and output voltage for inverting and non-inverting op-amp configurations. Ideal op-amp with infinite bandwidth and output swing. Real parts are limited by supply rails, gain-bandwidth product and slew rate.
How to use the Op-Amp Gain Calculator
- Enter or select configuration.
- Enter or select feedback resistor rf (ohms).
- Enter or select input/ground resistor rin (ohms).
- Enter or select input voltage (v).
- Read the calculated result; change any measurement to compare alternatives.
Formula
non-inverting: Av = 1 + Rf/Rin; inverting: Av = −Rf/Rin; Vout = Av × Vin; dB = 20log10|Av|
- config
- Configuration
- rf
- Feedback resistor Rf (ohms)
- rin
- Input/ground resistor Rin (ohms)
- vin
- Input voltage (V)
Ideal op-amp with infinite bandwidth and output swing. Real parts are limited by supply rails, gain-bandwidth product and slew rate.
Worked example
For op-amp gain calculator, the following measurements illustrate the exact method: Configuration: noninv; Feedback resistor Rf (ohms): 100000; Input/ground resistor Rin (ohms): 10000; Input voltage (V): 0.5.
Inputs
- ConfigurationNon-inverting
- Feedback resistor Rf (ohms)100000
- Input/ground resistor Rin (ohms)10000
- Input voltage (V)0.5
Result
- Voltage gain Av11
- Gain (dB)20.83
- Output voltage (V)5.5
Results explained
- Voltage gain Av
- Voltage gain Av from the formula above. Ideal op-amp with infinite bandwidth and output swing. Real parts are limited by supply rails, gain-bandwidth product and slew rate.
- Gain (dB)
- Gain (dB) from the formula above. Ideal op-amp with infinite bandwidth and output swing. Real parts are limited by supply rails, gain-bandwidth product and slew rate.
- Output voltage (V)
- Output voltage (V) from the formula above. Ideal op-amp with infinite bandwidth and output swing. Real parts are limited by supply rails, gain-bandwidth product and slew rate.
Frequently asked questions
Av = 1 + Rf ÷ Rin. With Rf = 100 kΩ and Rin = 10 kΩ the gain is 11, so a 0.5 V input gives 5.5 V out (supply rails permitting).
Av = −Rf ÷ Rin: the same resistors give −10, and the output is inverted in phase. The input impedance is approximately Rin, unlike the non-inverting input's very high impedance.
dB = 20 × log₁₀(|Av|) for voltage gain. Gain 11 is about 20.8 dB; gain 10 is exactly 20 dB.
The output cannot exceed the supply rails — most op-amps stop a volt or two short of each rail unless they are rail-to-rail types. Gain-bandwidth and slew rate also limit large, fast signals.
Roughly 1 kΩ to 1 MΩ: much lower wastes current and loads the output, much higher invites noise and bias-current errors. Keep Rf and Rin in that window and scale both together to change impedance without changing gain.