AMSA
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Hi guys, I have a question on folded cascode topologies.
We can choose between NMOS or PMOS mosfets for the input in the differential pair.
As we can see in several books, if we choose NMOST for the input in the differential pair, the current mirror on the cascode side is chosen to be NMOS. They can be a simple current mirror or a cascode current mirror. Since the topology presents a cascode (above) we choose the cascode current mirror too. That cascode current mirror can be simple or wide-swing.
So far so go.
What concerns to the PMOST for the input differential pair, the same applies but now the current mirror is above and the cascodes are in he lower side. The same applies here when it comes to choose the type of current mirror.
Those are the traditional folded cascode topologies. They come in almost all book in electronics.
However, I have seen a topology, where, for example, with PMOST in the input differential pair that the cascode current mirror is from a NMOS type and not PMOS, as it should, from my understanding and from what I have seen in books.
I did some more research and I saw that there are lots of handouts in some universities and in one book (BAKER's book) where they used this PMOST in the input differential pair and the current mirror with NMOST cascode. For example, in Baker's book, he has in page 803 (or something - 3rd Edition) a folded cascode amplifier with NMOST in the diff. input pair and the cascode current mirror with PMOST.
Can someone explain me what are the major or simply the differences between the "traditional" folded cascode and this kind of modified folded cascode version of the "traditional" folded cascode amplifier?
Drawback, advantages, major differences in performance, etc.
I can let here some pictures for reference:
Kind regards and thank you in advance.
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