(2) dirty/clean ground again [sdiy]

[Ian Fritz]

At 08:54 AM 8/20/2002, jhaible at debitel.net wrote:

>this is true - but only for DC. And at DC, the PSRR of most opamps is 
>excellent.

Sure -- as long as you are talking about decoupling resistors at each op 
amp. I was thinking more of the common practice of decoupling the whole 
board with one pair of series resistors.

BTW (according to Jung's Op-Amp Cookbook) PSSR is specified for symmetric 
changes in the PS voltages, so I think you might also need to consider how 
much current the amp is driving.

>For higher frequencies, the "power supply impedance" which the opamp sees
>is determined by the capacitors, i.e. rather low, regardless of the series 
>resistor.

Of course.


   Ian