Non-Inverting OP AMP Gain Calculator | Gain, Rf, Rin & Vout

How to use the non-inverting OP AMP calculator

To use the OP AMP calculator enter three values. The blank field will automatically be calculated. If you fill in all four fields, the last calculated value will be recalculated. You can modify the units using the selectors.

How a non-inverting OP AMP works

A non-inverting OP AMP stage produces an output with the same polarity as the input signal. In the ideal equation, the gain is set by 'Rf' and 'Rin' and is always greater than or equal to 1. In real circuits, the available output swing depends on the OP AMP supply rails, output stage limitations, input common-mode range, and load current. This means the equation predicts the ideal gain, but the real component can still saturate if you ask it to drive a voltage or current outside its limits. Non-inverting OP AMPs are widely used for buffering, signal conditioning, and modest voltage amplification. The non-inverting OP AMP equation is as follows:

A practical note: many common OP AMPs can only source or sink around 20 mA, sometimes less depending on the part. That is enough for signal work, but not for delivering useful power to a load. If what you really need is a stable supply rail or a current-hungry output, the voltage regulator calculator is a much better fit.

If you want to compare gain equations and sign inversion, take a look at the inverting OP AMP calculator. And if you are creating a bias or reference for the input, the voltage divider calculator usually enters the picture as well.

$$V_{out} = V_{in}\cdot\left(1+\dfrac{R_f}{R_i}\right)$$

Concept of Gain in OP AMPs

The gain of an OP AMP defines how much the input voltage is amplified at the output. In a non-inverting configuration, this gain depends on the ratio of Rf to Ri and is always greater than or equal to one. By selecting appropriate resistor values, it is possible to control the amplification level precisely. This makes OP AMPs useful in buffer stages, sensor interfaces, active filters, and preamplifier stages where signal amplitude needs to increase without phase inversion.

Example #1

You have an OP AMP in non-inverting configuration with 2[V] at the input. 'Rin' is 1k[Ω] and 'Rf' has a value of 3k[Ω]. What will be the value of 'Vout'?

• To calculate the output voltage we use the previous equation and substitute values: $$V_{out} = V_{in}\cdot\left(1+\dfrac{R_f}{R_i}\right) = $$ $$= 2\cdot\left(1+\dfrac{3000}{1000}\right) = 8[V]$$

Example #2

You are a guitarist who is fond of electronics and you want to make a homemade preamp. You know that your electric guitar outputs a signal with an amplitude of 50 m[Vrms]. You want to amplify that signal before sending it to a loudspeaker. For this, you decide to use an OP AMP in non-inverting configuration. If you want a 1[Vrms] signal at that next stage, what resistor configuration do you use?

• We can fix one of the two resistances to a value that is convenient for us and calculate the other. For example, we will set Rin to 1k[Ω]. Later, we isolate Rf from the equation and substitute: $$R_f = R_i\cdot\left(\dfrac{V_{out}}{V_{in}} - 1\right)= $$ $$= 1000\cdot\left(\dfrac{1}{0.05} - 1\right)= 19K[Ω]$$

Frequently Asked Questions

• Why use a non-inverting amplifier?
  It provides high input impedance and a positive voltage gain, meaning the output signal is in phase with the input.
• Can the gain be less than 1?
  No, the minimum gain for a non-inverting OP AMP configuration is 1 (unity gain buffer). If you need gain less than 1, you can add a voltage divider at the input.
• What is the input impedance of a non-inverting OP AMP?
  Ideally infinite. In practice, it is very high (Megaohms to Gigaohms), determined by the OP AMP's internal circuitry.
• What are common applications of non-inverting OP AMPs?
  They are widely used in audio amplifiers, signal conditioning circuits, and active filters due to their ability to amplify signals without phase inversion.