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Subject: What is CS/CD?CG Stage? what is coupling?

Date: 08/13/03 at 12:02 AM
Posted by: Lee
E-mail: myjasonlee[AT55]yaho.com (replace [AT55] with @ to reply)
Message Posted:

Hello Experts,

I came across the following statement
"The output impedance and the minimum required |Vds| of M2 is less strongly coupled than the value and voltage drop of a resistor. The voltage |Vds2,min| = |Vgs2-Vth2| can be reduced to even a few hundred milivolts by simply increasing the width of M2."

The circuit is M1(nmos) and M2(pmos) connected thru their drain where Vout is measured. M2 is connected to Vdd at source where M1 is connected to GND at source. Vb is applied at M2's gate while Vin is apply at M1's gate.

I do not understand the whole statement above. Can anyone explain for me? How do we get equation such that |Vds2,min| = |Vgs2-Vth2|?
And also the statement about increasing M2 width(any equation to explain for this)?

May I know how do we tell if a circut stage is a CS(common source), CG(common gate) or CD(common drain/source follower) ?

Kindly help me
Thanks a lot.

best regards and thanks
Lee

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