Differential Amplifiers

A differential amplifier is a type of electronic amplifier that increases the difference between 2 input voltages. Differential amplifiers also suppress and voltage common to the two inputs. A digital amplifier is one of the most used and important components within integrated circuits.

Differential Amplifier inputs

  • One inverting
  • One non-inverting

Why use a Differential Amplifier?

Differential amplifiers are used to amplify balanced differential signals which are used to communicate small signals in electrically noisy environments. The signal wires should be close or wired together and most of the induced noise with be “common mode”, affecting both wires in the same way.

Differential Amplifier Applications

The main application of a differential amplifier is to get rid of any noise and voltages that are present in both of the voltage inputs. This noise is present in common mode fluctuating voltage. Differential amplifiers are used in circuits that utilise negative feedback, controlling motors and signal amplification.

Various electronic devices use differential amplifiers

  • FM/Am Radio signal recovery
  • Audio pre-amplifiers
  • Microphone pre-amplifiers
  • TV Signal recovery
  • Digital to analogue converters

A Differential amplifier can be configured to operate as a single-ended amplifier by grounding one of the inputs.

Modern differential amplifiers normally sit on a single microchip. Inside the microchip, positive and negative signals are added and become a single output.

What is CMRR and PSRR?

CMRR – Common mode rejection ratio
PSSR – Power supply rejection ratio


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