Voltage-gain Amplifier Model

Discussion in 'Homework Help' started by mihosal, Apr 6, 2012.

  1. mihosal

    Thread Starter New Member

    Apr 6, 2012
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    Hello !!! I am attending a seminar in eectronics which has weekly exercises and labs.

    In this week's exercises, there is one that i could not achieve to deal with.

    So, I would like to ask for your help if it could be easy for you to deal with this exercise and help me filnish the assignment.

    The exercise appears in the pdf file attached !!

    Thanks in advance. !!!



    PS: THe Id if it is not appeared well is 0.18499498 Amperes
     
  2. panic mode

    Senior Member

    Oct 10, 2011
    1,319
    304
    don't mean to be rude but you are asking too much. it is unlikely that someone will do your homework for you. offering assistance is one thing but not doing everything. you need to try the exercise and ask specific question. the example is very simple, needs hardly anything above ohms and kirchoff's law. even equation for Id is given.

    example: finding Vo
    you know Vdd, RL and Id, (hint: just apply KVL)
     
  3. mihosal

    Thread Starter New Member

    Apr 6, 2012
    2
    0
    I am sorry :) You are not rude, but maybe i don't explain well !!! I just can't figure out the Δu0. The others I found it out, i thing that were apeared in pdf. I have found both V0 and Id, and trying a lot of figuring out the Delta u0 but can't achieve a result. !! Actually I need help only in this part, i the Delta u0
     
  4. panic mode

    Senior Member

    Oct 10, 2011
    1,319
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    Id is correct. solving KVL for gate circuit gives quadratic equation and two solutions:
    Id=0.185A
    Id=0.2262A
    first one is correct because second one creates too large voltage drop on Rs and transistor drops out of saturation.

    but how did you get 96.5V for Vo when Vdd=120V and Id=0.185A and RL=100 Ohm?

    back to your question:
    you could use small signal model (find gm etc.) or you can recalculate using what you already know. you will get different Id, which means different Vo then you just find difference between old and new result.
     
  5. WBahn

    Moderator

    Mar 31, 2012
    17,718
    4,788
    The typesetting on the pdf I am viewing is a bit hard to follow, but if I am following it correctly, you appear to have solved the first part of the problem where it is asking for the output voltage when the input bias voltage is 6.5V. Correct?

    Again, if I am following it correctly, the next part is simply asking you redo the first part but with the input bias voltage increased by 1V (so now it is 7.5V) and to report the answer in terms of how much the output voltage changed by.
     
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