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jo New Member Offline Posts: 1	PSRR Feb 25^th, 2006, 7:53pm Hi, I would like to simulate the PSRR of a simplest current mirror of gain one ? I put an AC voltage source on the VDD, but I have no logical result for the PSRR value. Someone can help me about a test bench proposal. Another question on the same topic is how to simulate the PSRR of an amplifier when it has a feedback.
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Andrew Beckett

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Bracknell, UK

Re: PSRR
Reply #1 - Feb 26^th, 2006, 7:47am

Not really sure what your problem is. Rather than using AC analysis, why not use spectre's xf analysis? This will compute the transfer function from any source (by default) to the specified output - and then you can choose which source to plot the transfer function after the simulation has completed.

It means you can do all your power-supply transfer functions at the same time as looking at signal transfer functions.

Regards,

Andrew.

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Raul

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Re: PSRR
Reply #2 - Mar 19^th, 2006, 8:31pm

Usually you want to simulate PSRR with the opamp in unity gain configuration. Since PSRR is defined as a change in input referred offset for a given change in supply voltage. An alternative is to see the ripple at the output and then refer it back to the input of the opamp given that you know what the closed loop gain is.
In certain cases like LDOs(low-dropout regulators) you just want to know how much ripple gets to the output of the regulator from the supply.

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regards, Raul Perez

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