Power Supply Rejection Ratio (PSRR)

A battery-powered application can see a change in power supply voltage of several hundreds of millivolts over the life of a product. Moreover, the op-amp is also often supplied from noisy lines and must, therefore, reject the noise adequately. For these reasons, it is important to know how a change or noise on the power supply manifests itself at the output of an op-amp.

It quantifies the amplifier’s sensitivity to power supply changes. Ideally, the Power Supply Rejection Ratio (PSRR) should be infinite. In other words, the power supply changes do not affect the output. Typical specifications for the PSRR of an amplifier range from 60 dB to 100 dB.

psrr.png

The picture below shows the MCP601 PSRR specification.

PSRRSpecs.png

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