Calculate voltage gain and output for operational amplifier circuits in inverting, non-inverting, and differential configurations. For inverting: Av = -Rf/Ri with input impedance equal to Ri. For non-inverting: Av = 1 + Rf/Rg with very high input impedance. For differential: Av = Rf/Ri applied to (V1 - V2). Reports gain in linear and dB, output voltage when input is provided, input impedance, and phase inversion status. Ideal op-amp assumptions (infinite open-loop gain, zero input bias current). Chain from ohms_law for power budgeting or resistor_color_code for component selection.

Op-amp circuit topology. 'inverting' uses Rf/Ri feedback with input to inverting terminal. 'non_inverting' applies input to non-inverting terminal with Rf/Rg feedback. 'differential' amplifies the voltage difference between two inputs.

Feedback resistor Rf in ohms. Sets gain magnitude in all topologies.

Input/gain resistor in ohms. For inverting: input resistor Ri. For non-inverting: ground resistor Rg. For differential: input resistor on both channels.

Input voltage in volts (optional). When provided, computes actual output voltage. For differential topology, this is V1 (non-inverting input).

Second input voltage in volts (differential topology only). This is V2 (inverting input).