# Differential Amplifier Calculator

### Unipolar to Bipolar Converter Example

If you need to design a differential amplifier, here is a handy calculator. All you need to define are the input range, the output range and a choice of voltage reference.

The differential amplifier was explained in different articles on this website. Solving the Differential Amplifier – Part 1, Part 2 and Part 3 shows a numerical example and how to design such an amplifier. Also, the common mode voltage level and the common mode output error were explained in the series of articles The Differential Amplifier Common-Mode Error – Part 1 and Part 2.

Enter the input range, Vin1 to Vin2, the output range, Vout1 to Vout2 and a reference voltage Vref. You need to choose two resistors, R2 and R3. The calculator will compute R1 and R4.

Given Input Range

 Vin1 = V Vin2 = V

Required Output Range

 Vout1 = V Vout2 = V

Choose a Reference Voltage

 V2 = V

Choose R2 and R3

 R2 = kOhm R3 = kOhm

Calculate R1 and R4

 R1 = kOhm R4 = kOhm

The default values for this calculator are set for a unipolar to bipolar converter. An explanation of this circuit and another example can be found in Design a Unipolar to Bipolar Converter for a Unipolar Voltage Output DAC. This calculator solves a system of 2 equations with 2 unknows, R1 and R4. Such a system will always have a solution, but the solution might not be physically possible. For example, if one of the resistors is negative, you will need to change the input data. Usually, changing the reference voltage will bring the resistors in the positive realm.

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