# transfer function in small signal mosfet model

Discussion in 'Electronic Design' started by Matteo, Apr 8, 2007.

2. ### Jim ThompsonGuest

Sure can. However I won't. If you can't do loop and nodal analysis
you should choose another trade.

...Jim Thompson

3. ### Jim ThompsonGuest

See....

Newsgroups: alt.binaries.schematics.electronic
Subject: transfer function in small signal mosfet model (from S.E.D) -
TransferFunctionSED.pdf
Message-ID: <>

...Jim Thompson

4. ### MatteoGuest

thank you very much Jim! I used nodal analysis as you suggested and I
got an enormous transfer function! Hope it's right..
do you know about some good book about the project of analog radio
frequency amplifiers where I can find examples and theory?

thanks again and sorry for my english

5. ### Jim ThompsonGuest

I wouldn't expect an "enormous transfer function". Post your work.

...Jim Thompson

6. ### MatteoGuest

Il Thu, 12 Apr 2007 09:44:33 -0700, Jim Thompson ha scritto:
here is my work ..hope it's allright! but I don't think so
http://www.thebags.it/listing/ampli/fdc0001.PDF

7. ### The PhantomGuest

I notice that you morphed Rd into Ro at the beginning of all the algebra;
I'll stick with Rd.

There is more than one kind of transfer function, such as the short circuit
transfer admittance and the open circuit transfer impedance, etc., but I
assume that what you want is the voltage transfer ratio.

The numerator is:

-gm Rd + Rd Cgd s

The denominator is:

( Cds ( Cgd + Cgs ) - Cgd ( 2 Cgd + Cgs )) Rd Rs s^2

+ ( Cds Rd + Cgs Rs + Cgd ( Rs - Rd + gm Rd Rs )) s + 1

One of us made a mistake in the algebra! :-(

8. ### Jim ThompsonGuest

And I dropped an "S" in my first page start :-(

...Jim Thompson

9. ### MatteoGuest

Il Thu, 12 Apr 2007 14:19:30 -0700, The Phantom ha scritto:
can you check your denominator? because mine is:

( Cds ( Cgd + Cgs ) + Cgd Cgs ) Rd Rs s^2

+ ( Cds Rd + Cgs Rs + Cgd ( Rs - Rd + gm Rd Rs )) s

+ 1

thanks!

10. ### The PhantomGuest

I carefully checked and found that I had made a single sign error. I agree
with your result with the exception of a single sign, which I have
indicated.
I get a plus sign here: ...Rs + Rd...

11. ### MatteoGuest

The Phantom ha scritto:
I carefully checked again and I get a plus sign too!
thank you very much for the help!

matteo