Power Supply Noise Rejection Ratio's (PSRR)

Dr.H

Member
2002-04-08 6:41 pm
Does anyone have access to info on PSRR for logic chips like 74HC74, etc? I have seen suggestions that these figures are as low as 6dB and therefore these chips benefit greatly from the use of clean power supplies.

Can anyone confirm this? Any data I can see?
Thanks
Ryan
 
Jocko Homo said:
There are no data sheets to back that up. Just the assumption that the P- and N-channel devices are idntical. If they are not, then it is more than 6 dB in one direction, and much less in the other.

(Hint: It acts like a voltage divider.)

Jocko

My measurements on various manufacturers show indeed about 6 dB. Jocko, most outputs are made symmetrical by scaling the FETs such that N and P side become "identical".