Op-Amp Calculator

Calculate voltage gain and output voltage for all standard operational amplifier configurations.

Inverting Amplifier

Input is applied to the inverting (−) input via R_in. Output is phase-inverted.
Gain A = −R_f / R_in

Non-Inverting Amplifier

Input applied to the non-inverting (+) input. Output is in phase with input.
Gain A = 1 + R_f / R_1

Voltage Follower (Buffer)

Output follows input exactly: V_out = V_in, Gain = 1
Provides high input impedance and low output impedance — ideal buffer.

Inverting Summing Amplifier

Sums multiple inputs with individual gains.
V_out = −R_f × (V1/R1 + V2/R2 + V3/R3)

Difference (Subtractor) Amplifier

Amplifies the difference between two inputs.
For R1=R3, R2=R4: V_out = (R2/R1) × (V2 − V1)

📐 Op-Amp Configuration Summary

Inverting

A = −Rf/Rin
Vout = A × Vin
Input Z ≈ Rin

Non-Inverting

A = 1 + Rf/R1
Vout = A × Vin
Input Z ≈ ∞

Follower

A = 1
Vout = Vin
Buffer, Z_in ≈ ∞

Summing (inv.)

Vout = −Rf·(V1/R1
+ V2/R2 + V3/R3)

Difference

Vout = R4/(R3+R4)
×(1+R2/R1)×V2
−(R2/R1)×V1

❓ FAQ

What is the difference between inverting and non-inverting amplifiers?

The inverting amplifier applies the signal to the negative (−) input, resulting in a phase-inverted output with gain −Rf/Rin. The non-inverting amplifier applies the signal to the positive (+) input, giving an in-phase output with gain 1+Rf/R1 (always ≥ 1).

Why does output clipping occur?

Op-amps cannot output a voltage beyond their supply rails (±Vs). When the calculated Vout exceeds ±Vs, the output saturates (clips) at approximately ±(Vs − 1.5V) for most op-amps, or very close to ±Vs for rail-to-rail op-amps.

What value should the bias current compensation resistor be?

For minimum offset voltage due to bias currents, add a resistor from the (+) input to GND equal to the parallel combination of Rin and Rf (for inverting) or R1 and Rf (for non-inverting). For FET-input op-amps this is usually unnecessary.