ConverterHub

Op-Amp Gain Calculator

Find op-amp inverting and non-inverting gain.

Result

5.70
-4.70

How it is calculated

For an ideal op-amp with negative feedback, the voltage gain is set by two resistors. The tool shows both configurations: non-inverting gain = 1 + Rf ÷ Rin and inverting gain = −Rf ÷ Rin. Rf is the feedback resistor from output back to the inverting input, and Rin is the resistor at the input. Both go in the same unit (ohms, kilohms, it does not matter as only the ratio counts). Rf cannot be negative and Rin must be above zero. The negative sign for the inverting case means the output is flipped (180° phase shift). Gain is a plain ratio, not decibels, and it assumes an ideal amplifier with no gain-bandwidth limit, no output saturation and no loading.

Worked example

Choose Rf = 47,000 Ω and Rin = 10,000 Ω. The ratio is 47,000 ÷ 10,000 = 4.7. Non-inverting: 1 + 4.7 = 5.70. Inverting: −4.7, shown as -4.70. So a 1 V input signal comes out near 5.7 V in the non-inverting circuit, or about −4.7 V in the inverting one, as long as the supply rails allow it.

Try this example →

Common mistakes

  • Using the non-inverting formula for an inverting circuit, or the reverse. The two differ by the 1 and by the sign.
  • Expecting a non-inverting gain below 1. Since gain is 1 + Rf ÷ Rin, it can never be lower than 1; use a divider before the input if you need to attenuate.
  • Forgetting that output is limited by the supply. A gain of 5.7 on a 3 V input cannot produce 17 V from a 12 V supply.
  • Confusing gain with decibels. A gain of 5.7 is about 15 dB, which is not the same number.
  • Mixing units, with Rf in kilohms and Rin in ohms, which throws the ratio off by a factor of 1,000.

About this calculator

This calculator finds closed-loop gain for the two basic op-amp configurations using the ideal op-amp approximation — infinite open-loop gain and input impedance, which forces the two input terminals to sit at the same voltage (a "virtual short"). For the non-inverting configuration, gain is Av = 1 + Rf/Rin; for the inverting configuration, gain is Av = −Rf/Rin, with the negative sign showing the output is 180° out of phase with the input. Both follow from applying Kirchhoff's current law at the inverting input node.

Electronics engineers use these formulas constantly when designing audio preamps, sensor signal-conditioning circuits, and instrumentation amplifiers, since picking two resistor values sets the gain directly without touching the op-amp itself. Hobbyists prototyping analog circuits and electrical engineering students learning feedback theory rely on the same pair of equations to size Rf and Rin for a target gain.

Was this helpful?

You can pick up to 3 reactions.

Comments (0)

  • Be the first to comment.

Popular calculators

Loan Calculator

Monthly payment, total interest and full amortization schedule.

Percentage Calculator

Percent change, percent of, and ratio calculations.

Discount Calculator

Calculate final price, savings, and discount amount.

BMI Calculator

Body mass index from height and weight (metric or imperial).

Age Calculator

Compute your exact age in years, months and days from a birth date.

Compound Interest Calculator

Calculate the final amount and interest earned with compounding.

All Calculators