Noise on op-amp supply

[vortex3]

When I use an operational amplifier, for example, for an inverting amplifier, how important is to have a low level noise (ripple) on the power supply? In other words, should I expect to have the same ripple of the power supply on the output signal of the op-amp superimpose to the signal?

Thanks!

 

[barry]

If you read the specs for an opamp you'll see a parameter called PSRR (Power Supply Rejection Ratio). This tells you the effect on the output that deviations on the supply have. The higher the number, the better rejection you'll have.

 

[chuckey]

The PSRR, can be very high like 60+ Db (1000:1), BUT if you have any bias networks strung across the Vcc rail to earth, the ripple at the tapping point (Vcc ripple/2) will be amplified by the amplifier, so decouple these points.
Frank