Differential Amplifier Calculator

A differential amplifier is an op-amp circuit that amplifies the voltage difference between two input signals — widely used in sensor interfaces, audio equipment, and noise-rejection applications. Enter your four resistor values (R1, R2, R3, R4) and two input voltages (V1 inverting and V2 non-inverting) into the Differential Amplifier Calculator to find the Output Voltage. Secondary outputs include Differential Gain, and the voltages at the V+ (non-inverting terminal) and V− (inverting terminal).

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Results

Output Voltage

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Differential Gain

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V+ (Non-Inverting Terminal)

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V- (Inverting Terminal)

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Frequently Asked Questions

What is a differential amplifier?

A differential amplifier is an electronic circuit that amplifies the difference between two input voltages while rejecting signals common to both inputs. It's commonly built using operational amplifiers with four external resistors.

How do I calculate the gain of a differential amplifier?

The differential gain is calculated as (R2/R1) when the circuit is balanced (R4/R3 = R2/R1). For unbalanced circuits, the gain depends on both the differential input and common-mode rejection.

What happens if my resistor ratios are not matched?

Unmatched resistor ratios will result in poor common-mode rejection, meaning the amplifier will amplify common signals present on both inputs instead of rejecting them. This reduces the circuit's performance.

What is the ideal op-amp assumption used in these calculations?

The calculations assume an ideal op-amp with infinite input impedance, zero output impedance, infinite open-loop gain, and that the inverting and non-inverting inputs are at the same voltage (virtual short).

Can the output voltage exceed the supply voltage?

No, the actual output voltage is limited by the op-amp's supply voltages. If the calculated output exceeds these limits, the op-amp will saturate and clip the output signal.

How do I choose resistor values for my differential amplifier?

Choose R1 and R3 to set the input impedance (typically 10kΩ-100kΩ). Then select R2 and R4 to achieve the desired gain while maintaining the ratio R4/R3 = R2/R1 for good common-mode rejection.

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

In a pure inverting configuration, set V2 to 0V and use V1 as input. For non-inverting, set V1 to 0V and use V2. The differential amplifier responds to the difference V2-V1.