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Subject: Re: Differential Amplifier

Date: 08/25/03 at 10:52 AM
Posted by: Jason
E-mail: jason_class[AT55]yahoo.com (replace [AT55] with @ to reply)
Message Posted:

In Reply to: Re: Differential Amplifier posted by Russ Kincaid on 08/24/03 at 9:02 PM:

Hello Russ,

Thank you so much for answering my questions. You are a great expert.
I have something I am not clear of. Can you explain a little bit more about the following statement you have made...
"You could not do this with n-type because the drains have to go to VCC and driving the source would not be constant current. There could be some bandwidth advantage in using n-type for Q3 and Q4 because driving the source is low Z which minimizes drain-gate feedback. "

So does your statement imply nmos current mirror can be use for that circuit?
Also, can you explain more about drain has to go to Vcc to drive the source?
Does it mean it is a must for drain to connect straight to Vcc?
And also is it a must Vcc to drive the source for every circuit? Can Vcc use to drive a drain?

I have changed the original circuit to a new circuit using nmos current mirror(originally pmos current mirror) in the below page

http://www.geocities.com/jason_class/nmos_current_mirror.gif

I have written colourful(red and purple) value of voltage at certain nodes. Kindly advise me if my analysis is correct. If wrong, kindly let me know where and why.

I do not understand the concept you have imparted here. Kindly help me to understand. I am a beginner and am very appreciate all your help and efforts to guide and teach.
Thank you Russ.


Best reagrds and Thanks
Jason


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