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wide band operational amplifer

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Junus2012

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Dear friends,

I found this cell from analog library of my foundry, it is classified as wide band amplifier,

my question what the thing makes it wide band, what this architecture named so I can make further research on it

Thank you

Best Regards

wideband amp.png
 

It's ordinary Miller OTA working in class A-AB.
it is wideband because is not narrowband (it is not a joke).
Don't pay too much attention to names.

More precisely, this guy is WB because can work from dc to some frequency (maybe several MHz), while narrowband is by definition operating in narrow frequency range (bandpass filter transfer function with 3dB band being small part of center freq), like LC tank LNAs.
 
Not sure how wideband this can be. It is kind of a push-pull amplifier, but apart from that it is just a Miller compensated stage. The UGBW is still gm1/Cm as in regular OTAs. Since the output stage is push-pull, you get gm2=gmp+gmn or some portion of it, which has potentially the ability of pushing the non-dominant pole towards higher frequencies for better phase margin. But I'm not uite sure how well this works because the inputs of the second diff pair connect to points with unequal driving capability/voltage swing.
 
Dear friends,

Thank you for your reply,

I will try to simulate the circuit to see the bandwidth,

I am not surprised by the name of the circuit more than I didn't understand the structure of the circuit, he used the push pull amplier with starnge connection,

I see he is using three stage ampliifer, is that have a benifit on the ampliifer bandwidth ?
 

Practically, it is a two stage amplifier. The 1st stage feeds directly the NMOS in the output stage. And the second diff pair has very limited gain, probably in the order of 1, which means it is supposed to have high frequency poles and not really limit the frequency response of the main amplifier.
 
Dear friends,

I have simulated the circuit, the result is shown below,

This cell as I have mentioned before is provided by the foundary, from the simulation result it doesnt looks like it is described as a wide band amplifier, if I increase the bias current it zero will come inside the GBW range,
and by any way it has zero peak even before 0 dB,

what is you opinio ?

wb.png
 

Looks OK to me. Enough phase and gain margin, at least in that corner.
 
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