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Compliance Finalization

  1. Mar 20, 2014 #1
    Thank you for any help that you can offer.

    Did I answer the questions?

    1. The problem statement, all variables and given/known data

    What is the voltage compliance range of the current source?
    Between what range of RL values will the circuit function as a current source?

    https://scontent-a.xx.fbcdn.net/hphotos-ash3/t1.0-9/1488711_10151945891295919_440459508_n.jpg

    VB = 1.6V
    VE = 1.0V
    IE = 1.0mA
    IL = 1.0mA

    2. Relevant equations

    VLimit = VCC - ILRE
    VCE < V < VLimit

    ....................................................................... ......
    Minimum staturation voltage:

    VCE (Sat) = 0.1V
    ....................................................................... ..................
    compliance range is:

    VCE < V < VLimit
    ....................................................................... ..........................................
    VCE < V < VCC - ILRE
    ...............................................
    0.1V < V < 10V - 1V
    ..................................................
    0.1V < V < 9V
    ..................................................




    Between what range of RL values will the circuit function as a current source?

    The range of load resistors can be found by:

    iOUT = Vin/R
    .................................................................
    VCE/iE < R < (VCC - ILRE)/iL
    ..................................................................................
    0.1V/1.0mA < R < (10V - 1V)/1.0mA
    ................................................................
    100(ohm) < R < 9000(ohm)



    Are answers? Are there any errors located?

    Thanks again for your help.
     
    Last edited: Mar 20, 2014
  2. jcsd
  3. Mar 21, 2014 #2
    Can you tell me why you think that for RL<100R this current source won't work?
    Also calculate Vce for RL = 9K.
     
  4. Mar 21, 2014 #3
    So the ranges are incorrect?
     
  5. Mar 21, 2014 #4
    or correct?
     
  6. Mar 21, 2014 #5
    incorrect
     
  7. Mar 21, 2014 #6
    So the active region is not in between 0.1V and 9V
     
  8. Mar 21, 2014 #7
    If you assume that transistor is in saturation region for Vce<0.1V. In this case the active region (Vce range) is indeed between 0.1V and 9V. But still you have incorrect resistor range.
     
  9. Mar 21, 2014 #8
    Jony130 can you look at what I did and tell me where I went wrong?
     

    Attached Files:

  10. Mar 21, 2014 #9
    Vce voltage is not the voltage that "appears" across RL resistor.
    V_RL = Vcc - Vce - Ve. So for Vce = 0.1V --->V_RL = (10V - 0.1V - 1V) = 8.9V.
    And if Vce = 9V --->V_RL = ??
     
  11. Mar 21, 2014 #10
    I'm lost .

    I knew my answers were incorrect.

    V(limit) was said to be the maximum before saturation

    so the compliance voltage range is okay.

    the load resistance range is not

    so what do I do? Cause I don't get this now
     
  12. Mar 21, 2014 #11
    Do you see the difference between Vce voltage and voltage across RL resistor?
     
  13. Mar 21, 2014 #12
    Vce is a junction voltage, The voltage across RL is a branch voltage,

    But I don't understand this range business.

    What does range mean with respect to Vce and RL?
     
  14. Mar 21, 2014 #13
    Q1. What is the voltage across V_RL if Vce = 0.1V ?
    Q2. What is the voltage across V_RL if Vce = 9V ?
     
  15. Mar 21, 2014 #14
    See I confused because I wasn't given an RL value,

    Ic = Ie only during the active region so I have no currents,

    I'm stuck like a duck.
     
  16. Mar 21, 2014 #15
    You don't need to know RL value. First we need to know V_RL voltage range. Next we can use this range to find RL value. The only think you need is to find V_RL range by using KVL and find V_RL voltage.
     
  17. Mar 21, 2014 #16
    Vcc-(ILxRL) - Vce = 0

    10V-(IL x RL) -0.1 = 0

    9.9V -(ILxRL) = 0

    9.9V = ILxRL

    9.9V/IL = RL

    9.9V/1.0mA = RL

    9.9 k(ohm) = RL
     
  18. Mar 21, 2014 #17
    You forget about Ve voltage.
     
  19. Mar 21, 2014 #18
    Vcc-(ILxRL) - Vce -Ve = 0

    10V-(IL x RL) -0.1 - 1V= 0

    8.9V -(ILxRL) = 0

    8.9V = ILxRL

    8.9V/IL = RL

    8.9V/1.0mA = RL

    8.9 k(ohm) = RL

    So is this the lower or the upper limit?
     
  20. Mar 21, 2014 #19
    Finally, some good work.
    What do you think ?
     
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