Op-Amp Gain Bandwidth Product Calculator

Estimate required gain-bandwidth product, maximum closed-loop bandwidth, or maximum closed-loop gain for voltage-feedback op-amp circuits using the ideal single-dominant-pole GBW relationship.

The calculator separates signal gain from noise gain. This is especially important for inverting amplifiers, where closed-loop bandwidth is determined by noise gain rather than by signal gain magnitude alone.

Engineering tool

Op-Amp Gain Bandwidth Product Calculator

Calculate required GBW, maximum closed-loop gain, or maximum small-signal bandwidth using noise gain and the single-pole GBW approximation.

Calculator mode

Amplifier configuration

Target closed-loop bandwidth

Small-signal closed-loop bandwidth target for the amplifier.

Feedback resistor Rf

Feedback resistor in the non-inverting network.

Ground resistor Rg

Ground resistor from the inverting input to ground.

Required Gain-Bandwidth Product

1 MHz

Closed-loop bandwidth is based on noise gain in this model.

Result console

Required gain-bandwidth product: 1MHz
Noise gain used: 10V/V
Signal gain: 10V/V
Signal gain magnitude: 10V/V
Rf / Rg: 9ratio
Target closed-loop bandwidth: 100kHz
Formula used: GBWrequired = NG × BWtarget

This is the ideal single-pole minimum. Real designs may require additional bandwidth and stability margin.

Formula reference

Gain-Bandwidth Product Formula

These equations are first-order estimates for compensated voltage-feedback op-amps with an approximately constant gain-bandwidth product.

GBW ≈ NG × BWGBWrequired = NG × BWtargetBWmax = GBW / NGNGmax = GBW / BWtargetNon-inverting: Av = NG = 1 + Rf / RgInverting: Av = -Rf / RinInverting: |Av| = Rf / RinInverting: NG = 1 + Rf / Rin

Variable definitions

GBW: Gain-bandwidth product or unity-gain bandwidth in Hz
BW: Closed-loop small-signal bandwidth in Hz
BWtarget: Target closed-loop bandwidth
BWmax: Maximum estimated closed-loop bandwidth
NG: Noise gain, the gain that determines closed-loop bandwidth
NGmax: Maximum allowable noise gain for a target bandwidth
Av: Signal gain from input to output
|Av|: Signal gain magnitude
Rf: Feedback resistor in Ω
Rg: Ground resistor for a non-inverting amplifier in Ω
Rin: Input resistor for an inverting amplifier in Ω

Important Inverting Amplifier Note

For an inverting amplifier, closed-loop bandwidth is based on noise gain, not signal gain magnitude. An amplifier with Rf = 90 kΩ and Rin = 10 kΩ has |Av| = 9, but NG = 10. Using |Av| × BW would understate the required GBW.

Variable Description

GBW: Gain-bandwidth product, usually specified in Hz, kHz, MHz, or GHz.
BW: Closed-loop small-signal bandwidth for the selected amplifier configuration.
BWtarget: Desired closed-loop bandwidth used to estimate required GBW.
BWmax: Maximum ideal closed-loop bandwidth estimated from available GBW and noise gain.
NG: Noise gain, the closed-loop gain that sets bandwidth in this model.
NGmax: Maximum allowable noise gain for the available GBW and bandwidth target.
Av: Signal gain from circuit input to output.
|Av|: Magnitude of signal gain, especially useful for inverting amplifiers.
Rf: Feedback resistor from output to the inverting input.
Rg: Ground resistor used in non-inverting gain networks.
Rin: Input resistor used in inverting gain networks.

Worked Examples

Required GBW for Non-Inverting Amplifier

Rf = 90 kΩ, Rg = 10 kΩ, Av = NG = 10, BWtarget = 100 kHz

GBWrequired = 10 × 100 kHz = 1 MHz

Required GBW for Inverting Amplifier

Rf = 90 kΩ, Rin = 10 kΩ, |Av| = 9, NG = 10, BWtarget = 100 kHz

Correct GBWrequired = 10 × 100 kHz = 1 MHz, not 900 kHz

Maximum Bandwidth

GBW = 10 MHz, NG = 10

BWmax = 10 MHz / 10 = 1 MHz

Maximum Gain

GBW = 10 MHz, BWtarget = 1 MHz

NGmax = 10, non-inverting gain max = 10, inverting gain magnitude max = 9

Unity-Gain Buffer

Rf = 0 Ω, Rg = 10 kΩ, NG = 1, GBW = 5 MHz

Ideal BWmax ≈ 5 MHz; real unity-gain bandwidth must be checked in the datasheet

Direct Noise Gain

NG = 20, BWtarget = 50 kHz

GBWrequired = 20 × 50 kHz = 1 MHz

What Is Gain-Bandwidth Product

GBW approximates the product of closed-loop bandwidth and noise gain for many compensated voltage-feedback op-amps.

Open-Loop Gain

The op-amp open-loop gain falls with frequency, limiting closed-loop gain accuracy and bandwidth.

Closed-Loop Bandwidth

Closed-loop bandwidth is the small-signal frequency range supported for the selected noise gain.

Single-Dominant-Pole Approximation

The simple GBW model assumes one dominant pole and an approximately constant gain-bandwidth product.

Noise Gain

Noise gain determines bandwidth, input offset amplification, and loop gain behavior.

Signal Gain

Signal gain describes the desired input-to-output gain and can differ from noise gain.

Non-Inverting Amplifier Bandwidth

For non-inverting amplifiers, signal gain and noise gain are equal.

Inverting Amplifier Bandwidth

For inverting amplifiers, noise gain is one higher than signal gain magnitude.

Unity-Gain Bandwidth

Unity-gain bandwidth is often close to GBW but should be read in datasheet context.

Phase Margin and Stability

A bandwidth estimate does not prove stability or adequate phase margin.

Slew Rate vs GBW

GBW is a small-signal limit; slew rate controls large-signal output slope.

Full-Power Bandwidth

Full-power bandwidth depends on slew rate and output amplitude, not only GBW.

Input and Feedback Capacitance

Parasitic capacitance can change noise gain, phase margin, and high-frequency behavior.