Differential amplifier - definition
Differential amplifier - definition
Differential amplifier is a type of analogue amplifier, whose task is to amplify the difference of voltages between two signal inputs while maximally suppressing common components, i.e. equal voltages on both inputs. Thanks to this property, a differential amplifier is a basic component of many electronic systems requiring high noise immunity, such as measurement sensors, bridge amplifiers, signal transmission systems and input circuits of analogue-to-digital converters-digital converters.
An essential parameter describing the performance quality of a differential amplifier is the common-mode signal attenuation coefficient (CMRR - Common-Mode Rejection Ratio), which determines, how effectively the system is able to differentiate the differential signal from common mode interference. The higher the CMRR, the better the amplifier performs in environments with high levels of electromagnetic interference or in systems with long signal cables, where susceptibility to interference is a major concern.
Differential amplifiers can be implemented as discrete systems, based on pairs of transistors in a common base or common emitter arrangement, or as integrated circuits of instrumental amplifiers, providing high stability of parameters and high precision. A typical differential circuit consists of two inputs - inverting and non-inverting - and one output, at which an amplified signal appears that is the difference of the input voltages, multiplied by the gain.
The differential amplifier is used for.inter alia. in analogue circuits of A/D converters, in differential measurement systems (e.g. strain gauges), as an input stage for Operational Amplifiers and in systems eliminating ground noise and offset voltages. In combination with suitable filters and protections, it can operate under very demanding environmental conditions, while maintaining linearity and precision over a wide range of voltages and frequencies.
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