Next report - BJT polarization

Discussion in 'Homework Help' started by PsySc0rpi0n, Apr 11, 2014.

  1. ericgibbs

    Moderator

    Jan 29, 2010
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    This circuit configuration does compensate for changes, but you are forcing a Base current of 38uA.! Do not mix divider Base biasing and a fixed current source.

    The biasing resistor divider and the emitter resistor are normally used in this type of circuit, no fixed current source.

    Try your sims without the current source.
     
  2. PsySc0rpi0n

    Thread Starter Well-Known Member

    Mar 4, 2014
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    Hum, my mistake in the uploaded files!
    Going to upload them again in the other post!
     
  3. PsySc0rpi0n

    Thread Starter Well-Known Member

    Mar 4, 2014
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    I think files are ok now... By the names you can figure out which one is normal, beta = 100 and temp = 100.

    The normal and beta = 100 produces similar Ic(Vce) curves but the temp = 100ºC is a bit more faraway from the 2 first simulations.

    You said that because of Ib change, the plot would also change, but the 2 first sims has different Ibs and they are very similar.
    I was hoping to get the same from the temp = 100 plot!
     
  4. ericgibbs

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    This is what I get.

    Use .param temp 100
     
  5. PsySc0rpi0n

    Thread Starter Well-Known Member

    Mar 4, 2014
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    So the directive I have is wrong?

    I did like:

    Code ( (Unknown Language)):
    1. .temp 100
     
  6. ericgibbs

    Moderator

    Jan 29, 2010
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    I am getting an unexpected result, little puzzling,will check it out.

    EDIT:

    Ran the Temp from 20 to 100C is 10C steps as a check of .temp 100
    The top plot is at 100C
    Its what I would expect for the way the Base current has been fixed.

    You should decide which transistor parameter you want to plot and the method used to provide the Base current.
    Its getting a little confused in the way your circuits are configured.:rolleyes:
     
    Last edited: Apr 19, 2014
  7. PsySc0rpi0n

    Thread Starter Well-Known Member

    Mar 4, 2014
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    The method has been always the same.

    Simulate the circuit as it is, then change β to 100 and simulate and last is to change temp to 100ºC and simulate again.

    When I change the β to 100, I recalculate Ib for that β and run the simulation.
    Then I just change temp to 100ºC and sun simulation. So i have 3 curves.

    Then I have to overlay those 3 curves and draw the Load Line.
     
  8. PsySc0rpi0n

    Thread Starter Well-Known Member

    Mar 4, 2014
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    Well, I have finished the report... Now I'm going for the lab part of the work!
     
  9. ericgibbs

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    Jan 29, 2010
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    Hi,
    I hope the report goes well.:)
    E
     
  10. PsySc0rpi0n

    Thread Starter Well-Known Member

    Mar 4, 2014
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    I can send it to you if you want to take a sneak peak at least to see the screens and calculations!
     
  11. ericgibbs

    Moderator

    Jan 29, 2010
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    Hi,
    I am sure many fellow students would find reading your Report useful.
    E
     
  12. PsySc0rpi0n

    Thread Starter Well-Known Member

    Mar 4, 2014
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    I was just telling that i can send it to you just to look for the screens and calculations as it is written in portuguese, so maybe not of big interest sending it here to forum.
     
  13. JoeJester

    AAC Fanatic!

    Apr 26, 2005
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    If you use the ideal transistor with all the default parameters, changing just the bf will produce the desired results.
     
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