1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Differential Mode Gain and 1/2 circuit

  1. May 31, 2015 #1

    perplexabot

    User Avatar
    Gold Member

    Hey all! I have been trying this problem for a while and can't seem to get the same answer as the solution. If someone can tell me where I am going wrong, that would be much appreciated. I am very close to the solution, but I am missing a term in the denominator. Everything is shown below! Thank you for your time.
    1. The problem statement, all variables and given/known data
    crkt_andQ.png

    2. Relevant equations (the solution from the solution manual)
    theSol.png

    3. The attempt at a solution
    myT.png

    I am getting stumped. Please help : /
    Thanks for reading.
     
  2. jcsd
  3. Jun 2, 2015 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    Since the two halves are coupled both at the emitters and collectors I would not try to use the "1/2 d.m. model" at all. Write the usual equations, I would go with kvl (actually I just sum currents to zero at every dependent junction which is basically the same set of equations.)

    If you HAVE to use the d.m model I cannot be of help.
     
  4. Jun 2, 2015 #3

    perplexabot

    User Avatar
    Gold Member

    Hmmm, ok. I will consider trying without half circuits. I don't have to use the 1/2 crkt model, I just thought it would be easier.

    Thank you
     
  5. Jun 2, 2015 #4

    rude man

    User Avatar
    Homework Helper
    Gold Member

    It would have been except for RL and RE.
    I will keep the answers to myself until you come up with your answers, then let you know how they look.
     
  6. Jun 2, 2015 #5

    perplexabot

    User Avatar
    Gold Member

    Ok, thank you. I'm in the middle of finals week, I will post an answer, just not too soon. I appreciate your help.
     
  7. Jun 2, 2015 #6

    rude man

    User Avatar
    Homework Helper
    Gold Member

    ???
    Different thread.
     
  8. Jun 2, 2015 #7

    perplexabot

    User Avatar
    Gold Member

    Lol, I wonder where that quote came from?! That is weird, I was trying to quote your previous reply. My reply is still valid, except the quote is wrong. Let me try and remove it. I apologize for that.
     
  9. Jun 2, 2015 #8

    rude man

    User Avatar
    Homework Helper
    Gold Member

    No prob.
    Actually a pretty involved analysis. 7 equations, 7 unknowns.
    For c.m. gain a hint: consider symmetry!
     
  10. Jun 2, 2015 #9
    The main problem I see is that you have calculated the voltage across RE/2 using the voltage divider formula applied to the input voltage Vi. But the current into RE/2 isn't just the current flowing down through rπ; you also have to include the current flowing down from the dependent current source, so you can't just use the voltage divider formula.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Differential Mode Gain and 1/2 circuit
  1. Differential mode gain (Replies: 12)

Loading...