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claire New Member Offline Posts: 5	PSRR of an AOp Jun 27^th, 2008, 11:41am Hi, I'm designing an AOp, wtih the software Cadence, and I would like to calculate the power supply rejection ratio of my ampli op. I manage to measure it, but it's not big enough, so I would like to have the formula which give the PSRR, to know what I have to change in my circuit....??? Someone can help me??
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sheldon

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Posts: 751

Re: PSRR of an AOp
Reply #1 - Jun 27^th, 2008, 7:16pm

Claire,

In general parameters such as power supply rejection are
dependent on the circuit architecture. So it would be useful for
people trying to help you if you provide the circuit schematic
or netlist. Also, it might be useful to provide a more detailed
description of the specification, for example, 80dB of rejection
at dc, ... Finally, it might be useful if you provided more
information such as positive or negative power supply
rejection. A little more information would be useful in order
to respond to your request.

Best Regards,

Sheldon

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HdrChopper

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Posts: 493

Re: PSRR of an AOp
Reply #2 - Jun 27^th, 2008, 7:49pm

Hi Claire,

Sheldon is right about being a little bit more specific on what he mentioned if you want some help on this. Nevertheless - and as a very general and basic outline - the PSRR is always proportional to the (differential) open loop gain of your amplifier and inversely proportional to the gain measured from the power supply to the output.
The first one is usually the one evaluated for stability and other purposes, while the second one is highly dependent on the architecture, as Sheldon suggested.

Let�s wait for more details for a more precise answer....

Regards
Tosei

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Keep it simple

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midou New Member Offline Posts: 5 TUNISIA	Re: PSRR of an AOp Reply #3 - Jul 2^nd, 2008, 3:30am hay Claire, I want to give you a good document that will help you to design your AOp.. but it is very large (more than 1000KB) so, how I can help you.. ;)
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claire New Member Offline Posts: 5	Re: PSRR of an AOp Reply #4 - Jul 8^th, 2008, 5:23am Thanks for your help, I've found the answer!!! Like you said, the PSRR of an AO is high, 80 dB for mine. So, all is working very well!!! Thanks again
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