Op Amp Gain Calculator
Calculate voltage gain, output voltage, and dB gain for inverting and non-inverting operational amplifier circuits.
Select the amplifier configuration, enter the resistor values and input voltage, and get instant gain and output calculations for your op amp circuit.
Op Amp Gain Calculator
Calculate voltage gain, output voltage, and dB gain for inverting and non-inverting operational amplifier circuits.
About the Op Amp Gain Calculator
An operational amplifier — commonly called an op amp — is a high-gain electronic voltage amplifier with a differential input and, usually, a single-ended output. Op amps are the building blocks of countless analog circuits: audio amplifiers, active filters, signal conditioners, integrators, differentiators, comparators, and precision voltage references, to name just a few. Understanding and calculating their gain is a core skill in analog electronics design.
The gain of an op amp circuit is set by external feedback resistors, not by the op amp's own open-loop gain (which is typically enormous, from tens of thousands to millions). Two fundamental configurations dominate practical circuit design.
In the inverting amplifier configuration, the input signal is applied to the inverting (minus) terminal through a resistor Rin, and a feedback resistor Rf connects the output back to the same inverting terminal. The non-inverting (plus) terminal is tied to ground. Under ideal op amp assumptions — infinite open-loop gain, infinite input impedance, zero output impedance — the voltage gain is Av = –Rf / Rin. The negative sign means the output is 180 degrees out of phase with the input. If Rf = 10 kΩ and Rin = 1 kΩ, the gain is –10, meaning a 1 V input produces a –10 V output.
In the non-inverting amplifier configuration, the input signal is applied directly to the non-inverting (plus) terminal, and the feedback network (Rf from output to the inverting terminal, and Rin from the inverting terminal to ground) sets the gain without inverting the phase. The ideal voltage gain is Av = 1 + Rf / Rin. With the same resistors (Rf = 10 kΩ, Rin = 1 kΩ), the gain becomes +11 — non-inverting and slightly larger than the inverting case because the input is directly buffered by the op amp before the feedback is applied.
Gain is also commonly expressed in decibels: dB = 20 × log₁₀(|Av|). A gain of 10 equals 20 dB; a gain of 100 equals 40 dB. The dB scale is logarithmic, which makes it easy to add gains when amplifier stages are cascaded: 20 dB + 20 dB = 40 dB.
This calculator handles both configurations. Enter Rf, Rin, and optionally the input voltage, choose inverting or non-inverting, and the tool instantly returns the voltage gain, output voltage, and dB value. It is useful for initial design, circuit verification, and educational exploration of op amp behavior.
Op Amp Gain Examples
Common inverting and non-inverting amplifier configurations with calculated gains.
| Configuration | Voltage Gain | dB Gain |
|---|---|---|
| Inverting: Rf = 10 kΩ, Rin = 1 kΩ | Av = –10 | 20 dB (magnitude) |
| Non-Inverting: Rf = 10 kΩ, Rin = 1 kΩ | Av = +11 | 20.83 dB |
| Inverting: Rf = 47 kΩ, Rin = 4.7 kΩ | Av = –10 | 20 dB (magnitude) |
| Non-Inverting unity buffer: Rf = 0, Rin = ∞ | Av = +1 | 0 dB (voltage follower) |
| Inverting: Rf = 100 kΩ, Rin = 1 kΩ, Vin = 0.05 V | Av = –100, Vout = –5 V | 40 dB |
How to Use the Op Amp Gain Calculator
- Select Inverting Amplifier or Non-Inverting Amplifier from the Amplifier Type dropdown.
- Enter the feedback resistance Rf in ohms (e.g. 10000 for 10 kΩ).
- Enter the input resistance Rin in ohms (e.g. 1000 for 1 kΩ).
- Optionally enter the Input Voltage Vin to calculate the actual output voltage.
- Click Calculate to see the voltage gain (Av), output voltage, gain in dB, and the formula used.
Frequently Asked Questions
What does a negative gain mean for an inverting amplifier?
A negative gain means the output signal is inverted — it is 180° out of phase with the input. The magnitude of the gain still tells you how much the signal is amplified. An Av of –10 amplifies the signal ten times while also flipping its polarity.
How do I choose between inverting and non-inverting configurations?
Use the inverting configuration when you need signal inversion or when you want to sum multiple input signals (virtual ground summing junction). Use the non-inverting configuration when you need high input impedance or must preserve the signal phase.
What is dB gain and why is it useful?
Decibel gain (dB = 20 × log₁₀|Av|) uses a logarithmic scale that makes it easy to work with cascaded amplifier stages. Instead of multiplying gains, you simply add their dB values. It also matches the way human hearing perceives loudness.
Do these formulas assume an ideal op amp?
Yes. The formulas Av = –Rf/Rin (inverting) and Av = 1 + Rf/Rin (non-inverting) assume an ideal op amp with infinite open-loop gain, infinite input impedance, and zero output impedance. Real op amps introduce small deviations, especially near their bandwidth limits, but the ideal formulas are accurate for most practical designs.
What is the gain-bandwidth product?
The gain-bandwidth product (GBW) is a constant for a given op amp that relates closed-loop gain to usable frequency range. If an op amp has a GBW of 1 MHz and you set the gain to 10, the usable bandwidth drops to roughly 100 kHz. This calculator does not account for GBW; consult the op amp datasheet for high-frequency designs.
How do I achieve a gain of exactly 1 (unity buffer / voltage follower)?
In the non-inverting configuration, connect the output directly to the inverting input with no resistors (Rf = 0 and Rin = ∞, giving Av = 1 + 0 = 1). This configuration has extremely high input impedance and very low output impedance, making it ideal for buffering a signal without loading the source.