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Subject: HELP: Don't understand folded cascode

Date: 08/11/03 at 12:43 AM
Posted by: Too
E-mail: toowang[AT55]yahoo.com (replace [AT55] with @ to reply)
Message Posted:

Hello All Experts,

Good Morning!
I am just started my Analog IC design subject, I have lots of problems in understand concept introduce in lectures and books. I would like to ask about folded cascode.
Kindly look at the page at the following website.

http://www.geocities.com/toowang/folded_cascode.gif

From the circuit, I understand Current is split equally between Q1 and Q2. But may I know how we can tell(any equation?)Id3=Id4=Ibias1? Is it true the gate for Q11 & Q2 & Q4 are connected together?

Then may I know what is the goal for this circuits?

Kindly let me know the role for each part of the circuit(with equations);
1) Q1 and Q2: Is it the role just to divide the 2Ib equally?
2) Q3 and Q4: What are they for?
3) Q5 and Q6: What are they meant for?
4) Q7to Q10 : What are they for?

For this folded cascode, are all mosfets work in saturation region? Is there any hint or guide for student to know which operation region a particular mosfet or grouped of mosfet are in?

I know I have asked a lot of questions. But I really need help in understanding the basic circuit in order to follow the lectures. I read a few books and could not get much ideas. Kindly help me by explaining in details of the circuit and its operation so that I can start to analyse other circuit using the knowledge u have shown me here. I reeally wish you all can put in some time to help.
I really need help . Please
I thank you all in advance.

best regards and thanks
Too

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