Two-Stage Miller Op-Amps - Poles and Zeroes

[esdeath_123]

For a two stage miller operational amplifier like the one shown below, what are the poles and zeroes? Jespers' book include these equations but no matter what I do, my simulations do not match or is too far away from the expected output...



The equations in the book are as follows:



Are these equations correct? Because no matter how I manipulate the variables, I either end up with really less bandwidth and/or gain or the stability is only around 20 in my simuations, even though Jespers book supposedly assures that setting the zero a decade beyond the gain-bandwidth product should net a 60 degree phase margin at least...I did this but could not even achieve that....Or am I misunderstanding something?

 

[promach]

If this is not school homework, you can refer to my own opamp circuit implementation using others' topology

 

[sutapanaki]

Yes, equation are correct. It is easy to check what is going on. Get the gm's and gds's and the caps of the transistors of the transistors in the operating point, plug in the equations and see what you get. It is a basic amplifier and you should get a good hold of it before going to other topologies.

 

[frankrose]

I don't know which transistor has gm2 on the above figure, the zero frequency is rather gm6/Cm. Bit confusing, the gm2 above means probably gm of the 2nd stage, not gm of the diff. pair's M2 transistor.
P.E.Allen has a got explaination to these: **broken link removed**

 

[sutapanaki]

I don't know which transistor has gm2 on the above figure, the zero frequency is rather gm6/Cm. Bit confusing, the gm2 above means probably gm of the 2nd stage, not gm of the diff. pair's M2 transistor.
P.E.Allen has a got explaination to these: **broken link removed**

Of course, gm2 here means the gm of M6. There is no doubt.