In a differential amplifier configured as a subtractor, the output voltage is given by the difference between the two input voltages V1V_1V1 and V2V_2V2, scaled by the ratio of the resistances in the circuit.
The general formula for the output of a differential amplifier is:
Vo=(RFR1)(V1−V2)V_o = \left( \frac{R_F}{R_1} \right) (V_1 - V_2)Vo=(R1RF)(V1−V2)
Where:
- V1V_1V1 and V2V_2V2 are the input voltages,
- RFR_FRF is the feedback resistor,
- R1R_1R1 is the input resistor connected to V1V_1V1,
- R2R_2R2 is the input resistor connected to V2V_2V2.
For a subtractor configuration, the resistors R1R_1R1 and R2R_2R2 are typically equal, meaning the circuit subtracts the two input voltages and amplifies the difference. If R1=R2R_1 = R_2R1=R2, then the output simplifies to:
Vo=(RFR1)(V1−V2)V_o = \left( \frac{R_F}{R_1} \right) (V_1 - V_2)Vo=(R1RF)(V1−V2)
In summary:
- The differential amplifier configured as a subtractor is designed to subtract one input voltage from the other.
- The output is proportional to the difference between the input voltages, scaled by the ratio of the resistors.