Difference amplifier calculator

Calculate differential output, resistor-ratio mismatch and common-mode gain.

Schematic

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Results

Ideal output voltage1 V

Differential gain	10 V/V
Common-mode gain	0 V/V

Advanced results

V1 coefficient	-10 V/V
V2 coefficient	10 V/V
Non-inverting input	181.82 mV
Ideal rail headroom	14 V

How difference amplifier works

The amplifier subtracts the first input from a scaled second input. When R2/R1 equals R4/R3, equal voltages on both inputs cancel and the output is the difference multiplied by R2/R1. The general equation also handles unmatched resistor ratios.

V_{out}=\left(1+\frac{R_2}{R_1}\right)\frac{R_4}{R_3+R_4}V_2-\frac{R_2}{R_1}V_1

Ideal DC equations assume negative feedback and operation within the supply rails. The guest uses a generic op-amp model; finite gain, input loading, output current and saturation can change the simulated result.

Change the form inputs or click a component value on the schematic. Choose Try in CircuitSim to simulate the configured circuit.

Do the math

Selected input values
V1	100 mV
V2	200 mV
R1	10 kΩ
R2	100 kΩ
R3	10 kΩ
R4	100 kΩ
V3	15 V
V4	-15 V

Non-inverting node: $V_+=V_2\frac{R_4}{R_3+R_4}$
$200\,\mathrm{mV}\times\frac{100\,\mathrm{k\Omega}}{110\,\mathrm{k\Omega}}$
≈ 181.82 mV
Output voltage: $V_{out}=\left(1+R_2/R_1\right)V_+-\left(R_2/R_1\right)V_1$
$11\times 181.82\,\mathrm{mV}-10\times 100\,\mathrm{mV}$
≈ 1 V

Difference amplifier calculator

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Schematic

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How difference amplifier works

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