Non-Inverting Amplifier Calculator
The non-inverting amplifier is a fundamental operational amplifier circuit that boosts a signal without inverting it. Its gain is set by two resistors and is always at least one, and it offers very high input impedance, which makes it ideal for buffering sensors and high-impedance sources. Enter the feedback resistor, the ground resistor, and an input voltage; this calculator returns the closed-loop voltage gain, the gain expressed in decibels, and the resulting output voltage for the ideal op-amp model.
Non-inverting amplifier formula
Voltage gain = 1 + Rf / Rg
Output voltage = gain * input voltage
Gain (dB) = 20 * log10(gain)
Rf is the feedback resistor and Rg the resistor from the inverting input to ground, both in ohms. The output is in phase with the input and the gain is at least one.
Op-amp circuit context
- The non-inverting amplifier has a positive gain of at least one and keeps the output in phase with the input.
- Input impedance is very high because the signal drives the op-amp input directly.
- Setting Rf to zero gives a unity-gain voltage follower, an ideal buffer.
- The gain depends only on the resistor ratio, not on the op-amp's open-loop gain, when that gain is very large.
- Output is limited by the supply rails; the ideal result assumes the op-amp does not saturate.
Non-inverting amplifier: frequently asked questions
What is the gain of a non-inverting amplifier?
For an ideal non-inverting op-amp the closed-loop voltage gain equals one plus the feedback resistor divided by the ground resistor: gain = 1 + Rf / Rg. The output is in phase with the input and the gain is always at least one.
Why is the minimum gain one?
Because the gain formula is 1 + Rf / Rg, the smallest possible gain occurs when Rf is zero, giving a gain of one. With Rf at zero (or Rg infinite) the circuit becomes a unity-gain voltage follower, useful as a buffer.
How does it differ from the inverting amplifier?
The non-inverting amplifier applies the signal to the non-inverting input, so the output is in phase and the gain is positive and at least one. It also has very high input impedance. The inverting amplifier produces a negative gain and a lower input impedance equal to its input resistor.
What is the input impedance?
The non-inverting configuration presents a very high input impedance because the signal drives the op-amp's non-inverting input directly, which draws almost no current. This makes it ideal for sensors and high-impedance sources.
What is a voltage follower?
A voltage follower is a non-inverting amplifier with a gain of exactly one, achieved by connecting the output directly to the inverting input (Rf zero, Rg open). It copies the input voltage to the output while providing high input impedance and low output impedance.
Official sources
- NIST: SI electrical units, the volt and ohm (SP 811).
- NIST: Physical Measurement Laboratory (electrical metrology).
Reviewed by the CalculatorHub team, edited by James Graham, 17 June 2026. See our methodology.