transfer function in small signal mosfet model

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

  1. Matteo

    Matteo Guest

    Matteo, Apr 8, 2007
    #1
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  2. Matteo

    Jim Thompson Guest

    On 8 Apr 2007 08:35:32 -0700, "Matteo" <> wrote:

    >hi all
    >
    >I have some difficult in finding the transfer function between input
    >and output of this circuit..
    >
    >http://www.thebags.it/listing/ampli/Webcam-1176046394.png
    >
    >can you help me please?
    >thanks
    >
    >mat


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

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    America: Land of the Free, Because of the Brave
    Jim Thompson, Apr 8, 2007
    #2
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  3. Matteo

    Jim Thompson Guest

    On 8 Apr 2007 08:35:32 -0700, "Matteo" <> wrote:

    >hi all
    >
    >I have some difficult in finding the transfer function between input
    >and output of this circuit..
    >
    >http://www.thebags.it/listing/ampli/Webcam-1176046394.png
    >
    >can you help me please?
    >thanks
    >
    >mat


    See....

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

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    America: Land of the Free, Because of the Brave
    Jim Thompson, Apr 10, 2007
    #3
  4. Matteo

    Matteo Guest

    On 10 Apr, 01:14, Jim Thompson <To-Email-Use-The-Envelope-I...@My-Web-
    Site.com> wrote:
    > On 8 Apr 2007 08:35:32 -0700, "Matteo" <> wrote:
    >
    > >hi all

    >
    > >I have some difficult in finding the transfer function between input
    > >and output of this circuit..

    >
    > >http://www.thebags.it/listing/ampli/Webcam-1176046394.png

    >
    > >can you help me please?
    > >thanks

    >
    > >mat

    >
    > See....
    >
    > Newsgroups: alt.binaries.schematics.electronic
    > Subject: transfer function in small signal mosfet model (from S.E.D) -
    > TransferFunctionSED.pdf
    > Message-ID: <>
    >
    > ...Jim Thompson
    > --
    > | James E.Thompson, P.E. | mens |
    > | Analog Innovations, Inc. | et |
    > | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    > | Phoenix, Arizona Voice:(480)460-2350 | |
    > | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    > | http://www.analog-innovations.com | 1962 |
    >
    > America: Land of the Free, Because of the Brave


    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
    Matteo, Apr 12, 2007
    #4
  5. Matteo

    Jim Thompson Guest

    On 12 Apr 2007 08:35:08 -0700, "Matteo" <>
    wrote:

    >On 10 Apr, 01:14, Jim Thompson <To-Email-Use-The-Envelope-I...@My-Web-
    >Site.com> wrote:
    >> On 8 Apr 2007 08:35:32 -0700, "Matteo" <> wrote:
    >>
    >> >hi all

    >>
    >> >I have some difficult in finding the transfer function between input
    >> >and output of this circuit..

    >>
    >> >http://www.thebags.it/listing/ampli/Webcam-1176046394.png

    >>
    >> >can you help me please?
    >> >thanks

    >>
    >> >mat

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

    [snip]
    >
    >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


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

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    America: Land of the Free, Because of the Brave
    Jim Thompson, Apr 12, 2007
    #5
  6. Matteo

    Matteo Guest

    Il Thu, 12 Apr 2007 09:44:33 -0700, Jim Thompson ha scritto:
    >
    > I wouldn't expect an "enormous transfer function". Post your work.
    >
    > ...Jim Thompson


    here is my work ..hope it's allright! but I don't think so :p
    http://www.thebags.it/listing/ampli/fdc0001.PDF
    Matteo, Apr 12, 2007
    #6
  7. Matteo

    The Phantom Guest

    On Thu, 12 Apr 2007 17:41:11 GMT, Matteo <> wrote:

    >Il Thu, 12 Apr 2007 09:44:33 -0700, Jim Thompson ha scritto:
    >>
    >> I wouldn't expect an "enormous transfer function". Post your work.
    >>
    >> ...Jim Thompson

    >
    >here is my work ..hope it's allright! but I don't think so :p
    >http://www.thebags.it/listing/ampli/fdc0001.PDF


    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! :-(
    The Phantom, Apr 12, 2007
    #7
  8. Matteo

    Jim Thompson Guest

    On Thu, 12 Apr 2007 14:19:30 -0700, The Phantom <>
    wrote:

    >On Thu, 12 Apr 2007 17:41:11 GMT, Matteo <> wrote:
    >
    >>Il Thu, 12 Apr 2007 09:44:33 -0700, Jim Thompson ha scritto:
    >>>
    >>> I wouldn't expect an "enormous transfer function". Post your work.
    >>>
    >>> ...Jim Thompson

    >>
    >>here is my work ..hope it's allright! but I don't think so :p
    >>http://www.thebags.it/listing/ampli/fdc0001.PDF

    >
    >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! :-(
    >
    >

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

    ...Jim Thompson
    --
    | James E.Thompson, P.E. | mens |
    | Analog Innovations, Inc. | et |
    | Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
    | Phoenix, Arizona Voice:(480)460-2350 | |
    | E-mail Address at Website Fax:(480)460-2142 | Brass Rat |
    | http://www.analog-innovations.com | 1962 |

    America: Land of the Free, Because of the Brave
    Jim Thompson, Apr 12, 2007
    #8
  9. Matteo

    Matteo Guest

    Il Thu, 12 Apr 2007 14:19:30 -0700, The Phantom ha scritto:
    > 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! :-(


    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! ;)
    Matteo, Apr 13, 2007
    #9
  10. Matteo

    The Phantom Guest

    On Fri, 13 Apr 2007 07:14:00 GMT, Matteo <> wrote:

    >Il Thu, 12 Apr 2007 14:19:30 -0700, The Phantom ha scritto:
    >> 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! :-(

    >
    >can you check your denominator?


    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.

    >because mine is:
    >
    >( Cds ( Cgd + Cgs ) + Cgd Cgs ) Rd Rs s^2
    >
    >+ ( Cds Rd + Cgs Rs + Cgd ( Rs - Rd + gm Rd Rs )) s

    I get a plus sign here: ...Rs + Rd...
    >
    >+ 1
    >
    >thanks! ;)
    The Phantom, Apr 13, 2007
    #10
  11. Matteo

    Matteo Guest

    The Phantom ha scritto:
    > On Fri, 13 Apr 2007 07:14:00 GMT, Matteo <> wrote:
    >
    >> Il Thu, 12 Apr 2007 14:19:30 -0700, The Phantom ha scritto:


    >
    >> because mine is:
    >>
    >> ( Cds ( Cgd + Cgs ) + Cgd Cgs ) Rd Rs s^2
    >>
    >> + ( Cds Rd + Cgs Rs + Cgd ( Rs - Rd + gm Rd Rs )) s

    > I get a plus sign here: ...Rs + Rd...


    I carefully checked again and I get a plus sign too!
    thank you very much for the help!

    matteo
    Matteo, Apr 13, 2007
    #11
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