Op-Amp Gain Calculator

An operational amplifier with negative feedback forms a stable amplifier whose gain depends only on external resistors, not on the op-amp's internal gain. This is what makes op-amp circuits so practical: the gain formula is simple, predictable, and set by components you choose.

In the inverting configuration, the input signal connects through R1 to the inverting (−) input, and Rf provides feedback from the output to the same node. Gain = −Rf/R1. The negative sign means the output is phase-inverted. The input impedance is approximately R1, since the inverting input is a virtual ground.

In the non-inverting configuration, the input connects directly to the non-inverting (+) input, and the voltage divider R1/Rf sets the feedback. Gain = 1 + Rf/R1. The output is in phase with the input. Input impedance is very high (MΩ range), limited only by the op-amp itself.

Key Points

• Inverting: Gain = −Rf/R1, output is phase-inverted
• Non-inverting: Gain = 1 + Rf/R1, minimum gain is 1 (unity)
• Gain in dB = 20 × log₁₀(|Av|)
• Bandwidth decreases as gain increases (gain-bandwidth product)

Applications

• Signal amplification and conditioning
• Active filters (combined with capacitors)
• Audio preamplifiers
• Instrumentation and sensor interfaces