Non-inverting OP AMP gain calculator

How to use the non-inverting OP AMP calculator

To use 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 to use a non-inverting OP AMP (operational amplifier)

An OP AMP (also called operational amplifier) in non-inverting configuration allows to obtain an output voltage that is in phase (has the same sign) as the input voltage. The value of the input can be scaled, i.e. a gain can be applied to it, by adjusting 'Rf' and 'Rin'. Non-inverting OPAMPs are very useful as they allow you to source any voltage that is below the component supply and above of the input voltage. For example, if the OPAMP is powered at 12[V] and your input voltage is 3[V], by adjusting the resistors you can get any value between these two. The limitation that OPAMPs have is that they cannot deliver too much current. The most common is that its maximum rating is 10-30 mA. Therefore, they are useful for powering low consumption circuits. If you need to handle higher powers, you can use linear regulators or switching power supplies (DC/DC converters). Of course, you can also use alternating current (AC) at the input of the OPAMP. The non-inverting OPAMP equation is as follows:

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

Concept of Gain in OPAMPs

The gain of an operational amplifier 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 OPAMPs ideal for applications where signal strength needs to be increased without altering its phase, such as in audio amplifiers, and analog signal conditioning.

Example #1

You have an OPAMP 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 amplifier. You know that your electric guitar outputs a signal with an amplitude of 50 m[Vrms]. You want to amplify that signal a little before delivering it to the speaker, since it would be almost imperceptible. For this, you decide to use an OPAMP in non-inverting configuration. If you want a 1[Vrms] signal to reach the speaker, 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.