how to obtain good PSRR for two stage amplifier?

[alicia8283]

ahuja psrr

how to obtain good PSRR for two stage amplifier?
My stability is ok as i have put compensation cap at the 2nd stage..
thanks in advance..

 

[renwl]

psrr 2 stage

how to obtain good PSRR for two stage amplifier?
My stability is ok as i have put compensation cap at the 2nd stage..
thanks in advance..

a paper has explained it.
<<design techniques for cascoded cmos op amps with improved psrr and common-mode input range>> by david b.ribner & miles a.copeland

 

[pfd001]

psrr + two stage

Increasing the channel length of your second stage amplifying transistor will help you get bigger positive PSRR. You can check Allen's book on this issue

 

[sachinagg77]

Poor PSRR of the basic two stage op-amp can be attributed to the compensation capacitor.

Alternative compensation techniques such as Ahuja Compensation and Cascoded Miller Compensation will help achieve better PSRR performence at high frequencies.

I hope it helps.

With Regards
Sachin

 

[jinxingsun]

You can use the cascode structure.

 

[JT]

When using a class A output, use an nmos driver with a pmos output. This isn't noticeable in AC sim, because of the small signal linearization, but for transient PSRR simulations (takes a lot of time, but these include the non-linearities of the transistors)
this is clearly visible.

2nd tip is isolating your opamp from the supply, by
-cascoding
-using a extra regulator which supplies your opamp. This can easily boost your PSRR by 30..50 dB.

br, Jef