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Differential Amplifier - Differential Mode

Discussion in 'Electronics Homework Help' started by EEM, Jun 25, 2016.

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  1. EEM

    EEM

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    Jun 25, 2016
    Hello, I am hoping someone could help me with part B of this problem. I am not sure of the effects the resistor would have on the differential output gain.
    Also I have attached my solution to part A but I am uncertain if I derived it correctly.

    Any help would be appreciated !

    differentialamp.jpg
     

    Attached Files:

  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    is there a minimum and maximum current through Rc?
     
  3. EEM

    EEM

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    Jun 25, 2016
    No, there was none specified
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    look at the circuit with that question in mind.

    perhaps you could consider the minimum current through either Rc and the output voltage in that case.

    As the current through Rc increases what happens to the output voltage? What effect would a low vs high value resistor have?

    the answer to this question should be pretty intuitive
     
  5. EEM

    EEM

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    Jun 25, 2016
    To me it would make sense that the higher value the added resistor is, then the smaller the differential output gain.
    I've attached a proof for my understanding of part b. Does this look OK ?

    partb.jpg
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Does that mean that if the resistors were a minimum (i.e. both outputs tied to Vcc) that the gain would be at a maximum?
     
  7. LvW

    LvW

    604
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    Apr 12, 2014
    EEM - why do you start with part b) of the task?
    Does this mean that part a) is solved already?
    If not - start with a) because this opens the way to part b).

    By the way: Your result in post#5 is not OK (the right side of R3 is not grounded!)..
     
    Last edited: Jun 27, 2016
    (*steve*) likes this.
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