Op-Amp Gain Calculator
Inverting, non-inverting, and differential gain
Required Parameters
Waiting for input data...
Quick Answer
Non-inverting gain: G = 1 + Rf/Rg. Inverting gain: G = -Rf/Rin. Differential gain: G = Rf/R1 (when matched).
Design Notes
Op-amp gain is set by external resistors, not the op-amp itself. The Gain-Bandwidth Product (GBW) limits useful gain at high frequencies: at 10× gain with a 10 MHz GBW op-amp, bandwidth drops to 1 MHz. Use 1% or better resistors for precision gain stages. For gains >100, consider two cascaded stages to avoid bandwidth and stability issues.
Common Mistakes
- 1
Forgetting the sign inversion in inverting configurations — the output is 180° out of phase with the input.
- 2
Exceeding the GBW product — requesting too much gain at too high a frequency causes signal attenuation.
- 3
Not providing a DC bias path for the non-inverting input in AC-coupled designs.
Knowledge Base
What is the gain formula for a non-inverting op-amp?
Gain = 1 + Rf/Rg, where Rf is the feedback resistor and Rg is the ground resistor. The minimum gain is 1 (unity gain buffer, when Rf = 0). For example, Rf = 100kΩ, Rg = 10kΩ: Gain = 1 + 100k/10k = 11 (20.8 dB). The '+1' comes from the direct input path.
What is the gain formula for an inverting op-amp?
Gain = -Rf/Rin, where Rf is the feedback resistor and Rin is the input resistor. The negative sign indicates 180° phase inversion. Input impedance equals Rin. For Rf = 47kΩ, Rin = 10kΩ: Gain = -4.7 (output is inverted and 4.7× larger). Unlike non-inverting, gain can be less than 1 (attenuator).
What is gain-bandwidth product (GBW)?
GBW is constant for a given op-amp: GBW = Gain × Bandwidth. An op-amp with GBW = 10 MHz at gain 10 has 1 MHz bandwidth. At gain 100, bandwidth drops to 100 kHz. This is the fundamental speed-vs-gain tradeoff. Choose an op-amp with GBW ≥ 10× your required gain × bandwidth.
How do I build a differential amplifier?
Use four matched resistors: R1 from V1 to inverting input, Rf from inverting input to output, R2 from V2 to non-inverting input, Rg from non-inverting input to ground. When R1=R2 and Rf=Rg: Vout = (Rf/R1)(V2-V1). Match resistors to ≤0.1% for good common-mode rejection (CMRR).
What op-amp should I use for my project?
General purpose: LM358 (dual, cheap), TLV2372 (rail-to-rail). Precision: OPA2277 (low offset), AD8628 (auto-zero). High speed: OPA2356 (200MHz), AD8065 (145MHz). Low noise: OPA1612 (audio), ADA4896 (RF). Low power: MCP6001 (100µA), OPA379 (2.9µA). Always check: supply voltage range, input/output swing, GBW, slew rate, and input bias current.
Why is my op-amp output clipping or railing?
Common causes: (1) Output trying to exceed supply rails — use rail-to-rail output op-amps. (2) Input common-mode range violated. (3) Gain too high causing saturation from offset voltage. (4) No DC bias path for AC-coupled inputs. (5) Load impedance too low for the op-amp's output drive capability.
Related Engineering Tools
Attenuator Calculator
Tee, Pi, bridged-T, and reflection pads
dBm to Watts Conversion
RF power conversion both ways
Frequency to Wavelength Conversion
Convert frequency and wavelength with velocity factor
RMS Voltage Calculator
Convert RMS, peak, and peak-to-peak for sine waves