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How to improve my amplifier's PSRR?

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jeremy_zhu

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hello，everybody！i designed a r2r amplifier for low supply voltage(<1V)，my question is how to improve my PSRR (only 36dB),other characteristics is just ok. the attachment shows my output stage of the amplifier;M22,M23's L=1.5um in 0.25um process. structure problem or we can change some parameters of these transistors to achieve a little bit higher PSRR? big L of the output transistors? it seems not work.

https://obrazki.elektroda.pl/32_1179936038.gif
 

Re: amplifier's PSRR

Hi, I've found some papers.
Mainly poor PSRR in ur ckt is result of Miller capacitance influence.
Change output ckt. Choose solution by yourself.
 

amplifier's PSRR

hi,DenisMark! thank you for your suggestions!
1v supply voltage and other proper size of the transistors can get 66dB PSRR.but i want to make this opa works in the supply voltage of <1V .
any more detail comments ？
 

amplifier's PSRR

U've got 66dB at 1V, but only 36dB at <1V. It seems that some MOSes leaves saturation region.
How is low "<1V"? Does it meet condition Vdd>Vgs+2Vt?
Give more details if u want somebody to help u (Vt, min Vdd, Vss values, whole schematic if u can).
 

amplifier's PSRR

every mos is in saturation region except the MOS Mr(in linear region). my input stage consists of differential pair & current mirror.sorry, i couldn't post my whole schematic .i want to know what's the key points of the output stage that affect the PSRR. is it likely to depend on my input stage ? vt of 0.25um is about 0.5v &-0.6v for nmos and pmos respectively,Vdd is 0.9v or less,Vss ~0
 

amplifier's PSRR

anyhow ，thank you very much。i'll study these papers and try to find the solutions！
best regards！
 

amplifier's PSRR

psrr=vout/vdd/vin/vdd
 

Re: amplifier's PSRR

refer to Razavi'book , change the compensation point
 

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