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Help needed for assignment

Discussion in 'General Electronics Discussion' started by simie, May 9, 2010.

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  1. simie

    simie

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    May 9, 2010
    Pls could someone help me on this. Thanks!!
     

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  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    You have copied the question down incorrectly. The schematic is missing a line :)

    Fix that and it may become much clearer.
     
  3. simie

    simie

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    May 9, 2010
    hi, here is the correct diagram attached.
    answers which i figured out but not sure.

    a) circuit use for current amplifier/power amplifier circuit
    b) is it type A? How do I diffrentiate between all of the classes?
    c) d) I do not know how to calculate this??
    e) how to measure? i dont know.?
    f) capacitorC2 is to block DC current from the inpt and output and only allowing AC to pass. Is it right?

    I am a first year student and this is my quiz question and it carries 10% of my final result. somebody pls help me. Thanks. Your kindness is very much appreciated
     

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  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Do you have values for the various resistors? (important for Qc&d&f)

    a) I'm not certain that is what is required. I would describe is as "an _______ amplifier", where the blank is replaced by a word suggesting it's use (read the question carefully).

    b) Look at some class A, AB, B and C amplifiers (google for schematics if you have no examples). Is there anything you can see about the design of them that appears constant? Can you see any of those features in this circuit? I feel sure that this would have been covered in class (and therefore in your notes or text).

    e) Is that "total current" (the word "current appears to be missing)? What current is the sum of base and collector current? (again, refer to your notes, then decide how you can measure this current without disconnecting anything).

    f) you are describing C1 and C3. C2 is between stages. If it blocks DC, then is there something to block? Is there any reason to want to block this? (the resistor values are not necessary to answer this unless you're going to calculate things from first principles). This is the sort of thing were there may have been an exercise you were asked to do that would illustrate the issue -- a set of calculations you don't need to do again once you understand the principle.
     
  5. simie

    simie

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    May 9, 2010
    I am unsure to calculate for question c and d and my lecturer didnt give resitor values. so how do i go about doing it. I am lost...:-(. pls help
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Why don't you start with A, B, and E -- they are not dependant on the resistor values (neither is F, strictly speaking).
     
  7. simie

    simie

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    May 9, 2010
    a) two stage common emmitter amplifier circuit
    b) class A
    c)D i dont know
    d) how to measure i dont know also
     
  8. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    for (e), what is the relationship between the currents in the base, emitter, and collector?
     
  9. simie

    simie

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    May 9, 2010
    Ie=Ic + Ib
    and Ie=Ic
    vbe=0.7V
     
  10. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    The first and the second cannot both be true (at least not if there is any base current).
     
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