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From: farjamit@eecs.cs.pdx.edu (Tom Farjami)
Newsgroups: sci.electronics
Subject: A question about effect of offset voltage in trans-amps
Message-ID: <2644@pdxgate.UUCP>
Date: 17 May 91 04:11:51 GMT
Sender: news@pdxgate.UUCP
Reply-To: farjamit@eecs.cs.pdx.edu (Tom Farjami)
Organization: Portland State University, Portland, OR
Lines: 20

Greetings,

I have a question about effect of offset voltage in operation of
a simple 5 transistor trans-amp. I appreciate any comments in this regard.

Basically for a open loop trans-amp, vout = gain . (V+ - V-) + offset

However when we cause the unity feedback, that is when used as a follower,
math tells me that, Vout = ( gain /(gain +1) ) . Vin + offset/gain  

It seems too good to be true. My question is that would the offset be
divided by the gain of the open loop trans-amp or not ? How does offset
show up in the follower operation? . 

thank you.

Sincerely,

Tom Farjami
farjamit@eecs.ee.pdx.edu