help! freq compensation

[overmars]

Hi!
I'm working on an three-stage op-amp design, the basic functionality structure has been established, but where shall I put compensation ckt to make this op-amp stable? After the simulation,I found there were many poles and zeros.
I just don't know where the dominant pole lies and which ckt point is the best place to add compensation ckt.
Please help me, thank you in advance!

 

[rania_hassan]

Hi,
First I'd like to know why you are using three stage Amplifier?
Could you get the gain value you want with two stage only as it's easier in stability calculation?
Second you can see the "Design of Analog Integrated Circuits by Behzad Razavi
best regards,
Rania

 

[overmars]

Sorry, it's a two-stage op-amp.
I know some of this theory, but practically I don't know where usually those poles locates, so that I could make related compensation ckt.
Regards!

 

[rania_hassan]

Hi, If you used two stage amplifier you can just single ended OTA followed by common source & used miller compensation
read about poles splitting in Razavi
best regards,
Rania