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PSRR in DC is only -38dB- any ideas?

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chang830

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PSRR in DC

Hi,
I am designing an amplifier. I found the PSRR in DC is only -38dB in typ. I am trying to check out why it has so low PSRR.

Anyone pls. shed some light on it?

Thanks in advance
 

Re: PSRR in DC

chang830 said:
Hi,
I am designing an amplifier. I found the PSRR in DC is only -38dB in typ. I am trying to check out why it has so low PSRR.

Anyone pls. shed some light on it?

Thanks in advance
Click to expand...

it depend on your open loop gain of your opamp, try to increase it, you will get better psrr
 

    C

    chang830

    Points: 2
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Re: PSRR in DC

surianova said:
chang830 said:
Hi,
I am designing an amplifier. I found the PSRR in DC is only -38dB in typ. I am trying to check out why it has so low PSRR.

Anyone pls. shed some light on it?

Thanks in advance
Click to expand...

it depend on your open loop gain of your opamp, try to increase it, you will get better psrr
Click to expand...

In fact, my block is in closed loop work and has fixed gain of 6dB. I guess there is some leakage from supply to output, but how can I to foound it out? It has mitiple stage, so I don.t know how to check....

Thanks
 

Re: PSRR in DC

chang830 said:
surianova said:
chang830 said:
Hi,
I am designing an amplifier. I found the PSRR in DC is only -38dB in typ. I am trying to check out why it has so low PSRR.

Anyone pls. shed some light on it?

Thanks in advance
Click to expand...

it depend on your open loop gain of your opamp, try to increase it, you will get better psrr
Click to expand...

In fact, my block is in closed loop work and has fixed gain of 6dB. I guess there is some leakage from supply to output, but how can I to foound it out? It has mitiple stage, so I don.t know how to check....

Thanks
Click to expand...


just Ac=1 at power supply VDD
and run AC analysis, plot the vout/VDD, you will get psrr

but remember PSRR must run in closed loop.
 

Re: PSRR in DC

surianova said:
chang830 said:
surianova said:
chang830 said:
Hi,
I am designing an amplifier. I found the PSRR in DC is only -38dB in typ. I am trying to check out why it has so low PSRR.

Anyone pls. shed some light on it?

Thanks in advance
Click to expand...

it depend on your open loop gain of your opamp, try to increase it, you will get better psrr
Click to expand...

In fact, my block is in closed loop work and has fixed gain of 6dB. I guess there is some leakage from supply to output, but how can I to foound it out? It has mitiple stage, so I don.t know how to check....

Thanks
Click to expand...


just Ac=1 at power supply VDD
and run AC analysis, plot the vout/VDD, you will get psrr

but remember PSRR must run in closed loop.
Click to expand...

Yes, it can give me the PSRR value, but did not tell me why it is so low? Abd it also can not tell me what's the leakage path?

Any good method to help on ot?

Thanks
 

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