Differential Amplifiers

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

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 will 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, such as 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 also 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 do CMRR and PSRR stand for?

  • CMRR is the abbreviated version of Common Mode Rejection Ratio and refers to the power ratio of differential gains between the common-mode gain. This unit is measured in positive decibels.
  • PSRR is the abbreviated version of Power Supply Rejection Ratio and refers to an amplifiers ability to consistently maintain output voltage white the DC voltage supplied is varied.

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Description Price Power Supply Type Typical Single Supply Voltage Typical Dual Supply Voltage Maximum Input Offset Voltage Maximum Input Resistance Maximum Voltage Gain Typical Gain Bandwidth Product Minimum CMRR Output Configuration Number of Channels per Chip Mounting Type Package Type Pin Count Rail to Rail
RS Stock No. 822-5828
Mfr. Part No.LTC1992CMS8#PBF
Each (In a Pack of 2)
Dual, Single 2.7 → 11 V ±1.35 → ±5V ±2.5mV 500MΩ 80dB 3MHz - - 1 Surface Mount MSOP 8 Rail to Rail Output
RS Stock No. 193-5523
Mfr. Part No.MCP6D11-E/MS
Each (In a Tube of 100)
Single 2.5 V - - - - - - - - SMD - - -
RS Stock No. 197-7140
Mfr. Part No.INA117KU
Each (In a Tube of 75)
Dual 12 V ±15V 1000µV - - 200kHz - - 1 - SOIC 8 -
RS Stock No. 153-3196
Mfr. Part No.AD8390AACPZ-R7
Each (In a Pack of 2)
Dual, Single - - +3V - - 45MHz 58dB Differential 2 Surface Mount LFCSP 16 No
RS Stock No. 183-1989
Mfr. Part No.AD8475BRMZ
Each (In a Pack of 2)
Dual, Single 3 → 10 V ±1.5 to ±5V - 1.75kΩ - 150MHz 86dB Differential 1 Surface Mount MSOP 10 Rail to Rail Input/Output