PSRR or PSR, which is more important?

[suria3]

Hi guys,

I'm confused, in measuring the power supply rejection of a opamp, which measurement is more important, PSRR or PSR?

PSRR = Differential gain/ Power Supply gain = [Vout/Vin]/[Vout/Vsupply]

PSR = Vout/Vsupply

I'm asking this because some designer say PSR is more important, some say have to see overall PSRR....pls explain.

Suria

 

[iamxo]

as I know, PSR is usually defined to explain such as bandgap or LDO's power supply rejection, not to explain opamp's.

am I right?

 

[jc2]

I agree with iamxo. PSR is measured for reference sources, etc.

And PSRR is measured for OPAMPs.

 

[surianova]

I agree with iamxo. PSR is measured for reference sources, etc.

And PSRR is measured for OPAMPs.

do we measure psrr or psr for differential limiting amplifier?

 

[isaacnewton]

PSRR is the value of the power rejection refered back to the input.
For the regular, it doesn't really have input signal, so PSR is measured.
For the Opamp, there is an input, so ...

I agree with iamxo. PSR is measured for reference sources, etc.

And PSRR is measured for OPAMPs.