Power Supply Rejection Ratio(PSRR)

[natali]

Hello,
How can we calculate PSRR for a ring oscillator(which is realized using MOS)?

Thank you

 

[Harald Kapp]

The standard definition of PSSR is the log ratio of change in output voltage to change in input voltage of e.g. an operational amplifier or a voltage regulator.
This useless in your case. You are most probably interested in the change in oscillator frequency as a consequence of change in supply voltage. You can easily calculate the ration dFosc/dVsupply and use this as a definition for PSSR in your case. Note that unlike with voltages you cannot express this ratio in decibels because dFosc/dVsupply has a unit (Hz/V) wheras PSSR for an amplifier is unitless (units cancel when cyou calculate dVout/dVsupply).

I'm not sure whether that's the official definition - I know of none other.