A difference amplifier circuit, also known as a differential amplifier or subtractor amplifier, is an electronic circuit designed to amplify the difference between two input signals while rejecting any common-mode signal (signals that appear equally on both inputs). It is commonly used in various applications, including signal subtraction, noise cancellation, and instrumentation systems where precise measurement of the difference between two signals is required.
The primary function of a difference amplifier is to subtract one input signal from another, effectively providing the amplified difference between the two input voltages. The difference amplifier has two input terminals (usually labeled as "+Input" and "-Input") and an output terminal. The configuration of the circuit can vary, but a typical setup uses operational amplifiers (op-amps) to achieve the desired functionality.
Here's a simplified representation of a difference amplifier circuit using an operational amplifier:
lua
Copy code
R1 R2
+--/\/\----/\/\--+
| |
Vin+ |
| Op-Amp | Vout
Vin- +---->
| |
+------------------+
R3 R4
In this circuit:
Vin+ is the non-inverting input, and Vin- is the inverting input.
R1 and R2 set the gain of the amplifier for the +Input signal.
R3 and R4 set the gain of the amplifier for the -Input signal.
The output voltage (Vout) is the amplified difference between the voltages at Vin+ and Vin-.
The gain of the amplifier can be determined by the ratio of the resistance values: Gain = (R2 / R1) - (R4 / R3).
The main advantage of a difference amplifier is its ability to amplify the difference between signals while rejecting any common-mode noise or interference that may affect both input signals equally. This makes it useful for various applications, such as measuring the voltage drop across a sensor, subtracting a reference signal from a sensor output, or even cancelling out noise that appears in both signals.
In summary, a difference amplifier circuit is designed to subtract one input signal from another, amplifying the difference while rejecting common-mode signals. This circuit is widely used in electronics, instrumentation, and signal processing applications where precise signal subtraction is required.