A difference amplifier circuit, also known as a differential amplifier, is an electronic circuit that amplifies the difference between two input voltages while rejecting or attenuating any common-mode voltage that is present in both inputs. In simpler terms, it amplifies the voltage difference between two signals while ignoring any voltage that appears in both signals equally.
The primary purpose of a difference amplifier circuit is to extract and amplify the useful information contained in the voltage difference between two signals while eliminating any unwanted noise or interference that may be present in both signals. This makes it particularly useful in applications where you want to measure or amplify the difference between two sensor outputs, signals from different sources, or any scenario where you want to extract a meaningful signal while rejecting unwanted background noise.
The configuration of a basic difference amplifier circuit typically involves two input terminals (often labeled as "non-inverting" and "inverting" inputs) and an output terminal. The difference between the voltages at the two input terminals is amplified and appears at the output terminal. The gain of the amplifier (amplification factor) can be adjusted through external components like resistors in the circuit design.
Difference amplifier circuits find applications in various fields, including:
Instrumentation and Measurement: They are commonly used in measurement systems to accurately measure the difference between sensor signals while rejecting common-mode noise.
Biomedical Electronics: In medical devices, they can amplify the minute differences in bioelectric signals, such as ECG (electrocardiogram) or EEG (electroencephalogram).
Communication Systems: Differential amplifiers are used in communication systems to extract the modulated information signal while rejecting interference.
Audio Equipment: In audio circuits, they can be used to eliminate noise that is common to both audio channels, resulting in cleaner sound output.
Control Systems: They are employed in control systems to process differential feedback signals, helping to accurately control processes while ignoring common environmental disturbances.
Signal Processing: In various signal processing applications, difference amplifiers help in enhancing signal-to-noise ratios.
It's important to note that while difference amplifiers are designed to reject common-mode signals, they are not perfect and have limitations in terms of common-mode rejection ratio (CMRR) and performance. Design considerations and component selection are crucial to achieving the desired performance in different applications.