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Low power cascode structure question

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tony_wu_ad

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Dear all:

I have some trouble with learn about low power cascode structure, I have see some book, but none of them can give more advice and analyse about low power cascode structure.

Someone can give me some advice about this structure?

Thank you :)
 

tony_wu_ad

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mists said:
Thank you, I have down the book,

But some one can give me a paper about it ?

Thank you:)

Added after 3 minutes:

rajanarender_suram said:
look for this in Razavi book
I have read the Razavi book, but in this book, the shematic is too simple and I have not find a total schematic use low voltage cascode. I can not find bias part schematic, so I want search a total schematic.

Someone can help me ?:)

Thank you!
 

analog_prodigy

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It's looks wide swing cascode current mirror. If it is the case, then you can find it in both John martin and Grey&Meyer
 

amarnath

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its a simple high swing cascode, its used because in a simple current mirror the mirroring error due to vds mismatch is very high. But when you use a cascode structure the vds of the bottom(mirroring)transistor is being controlled by the cascode transistor and hence when this current is mirrored the mirroring error is going to be negligible.just put this circuit in cadence and try tweaking the sizes from the textbook sizes , you will understand what is happenning.


amarnath
 

tony_wu_ad

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analog_prodigy said:
It's looks wide swing cascode current mirror. If it is the case, then you can find it in both John martin and Grey&Meyer
Thank you :)

Added after 1 minutes:

amarnath said:
its a simple high swing cascode, its used because in a simple current mirror the mirroring error due to vds mismatch is very high. But when you use a cascode structure the vds of the bottom(mirroring)transistor is being controlled by the cascode transistor and hence when this current is mirrored the mirroring error is going to be negligible.just put this circuit in cadence and try tweaking the sizes from the textbook sizes , you will understand what is happenning.


amarnath
Thank you, I try it :)
 

analog_prodigy

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Yes, i tried this circuit earlier on a simulator. i got high output resistance as a cascode structure and withl little headroom
 

122013137

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Hi, amarnath
The conclusion of allen'book had been proved Iref=Iout when W1/L1 =W2/L2 =W3/3 =W4/L4 and Vbs=0~

But how should be Vds1=Vds3 at first? thanks
 

pmr9

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Yiu can find somuch data in books and papers for analysis. Iout and Iref need not have same value and its a high swing current mirror. analytically Gray and Holberg are better
 

ameed

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hi,


It's looks wide swing cascode current mirror. If it is the case, then you can find it in both John

martin and Grey&Meyer

also refer analog cmos design text book.
 

jjsnail

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i think razavi's book is enough
 

amarnath

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its simple, set the gate voltage of M2,M4, to 2vdsat+vth, so that vds of the mirroring transistors are equal.For generating this bias voltage of 2vdat+vth, you can use a transistor of 1/4 the width of M1,M2,M3,M4(assuming M1,M2,M3,M4 are of equal size).


Thanks
Amarnath
 

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