Op-Amp Calculator - Inverting, Non-Inverting & Difference Gain

Op-Amp Configurations

Inverting: Gain = −Rf / Rin. The output is inverted relative to the input.

Non-Inverting: Gain = 1 + Rf / Rin. The output is in phase with the input.

Difference: For a symmetric resistor network (R1=R3, R2=R4), the gain equals Rf / Rin and the output represents the amplified difference between two inputs.

Gain formulas summary

Bandwidth limitation

Every op-amp has a fixed Gain-Bandwidth Product (GBW): for a given device, Gain × Bandwidth = constant. This means higher closed-loop gain comes at the cost of usable bandwidth.

Example: the TL071 has GBW ≈ 3 MHz. At a closed-loop gain of 10, the −3 dB bandwidth is 300 kHz. At gain 100, bandwidth drops to 30 kHz. At gain 1000, only 3 kHz - too narrow for audio applications. Always check GBW against your required gain and signal frequency.

Active filter configurations

Op-amps enable active filters with gain and controllable frequency response, unlike passive RC filters which have insertion loss. Two common topologies:

• Sallen-Key: uses two RC stages and one op-amp in non-inverting configuration. Simple, low component count, good for low-Q (Butterworth) filters. Cutoff frequency: f_c = 1 / (2π√(R1·R2·C1·C2)).
• MFB (Multiple Feedback / Infinite Gain): uses one op-amp in inverting configuration with three passive elements in the feedback path. Better suited for higher-Q (Chebyshev) filters. More sensitive to component tolerances but provides more design flexibility.

Real vs. ideal op-amp differences