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Hhow an NPN transistor can be used as a small signal amplifier?

  1. Oct 18, 2007 #1
    Hi,

    Could someone please help me with something i need to know to complete my college course?

    The question says:

    'Show with the aid of a circuit diagram and input/output waveforms how and NPN transistor can be used as a small signal amplifier, when operating in a common emitter configuration (a simple common emitter amplifier)'


    I haven't the foggiest what this means and i have no way of asking my tutor. Anyone know anything about it?
     
  2. jcsd
  3. Oct 18, 2007 #2

    berkeman

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    Thread moved to Homework Help forums.

    Welcome to the PF, BoroBoy. What learning resources do you have? Surely you have a textbook? If not, there is always the web...here's wikipedia.org's entry:

    http://en.wikipedia.org/wiki/Common_emitter_amplifier

    And if you do a google search on common emitter amplifier tutorial, you will get lots of helpful hits. Why don't you try reading those resources a bit, and then feel free to post specific questions if any result from the reading.
     
  4. Oct 19, 2007 #3
    Cheers, got that one sorted now. Now i need help with another, it's a fairly straightforward question to understand what its asking for:

    'Show, using a circuit diagram how a 4-input AND circuit may be constructed using three 2-input AND gates. Your diagram should identify the intergrated circuit used and the pin connections.'
     
  5. Oct 21, 2007 #4

    malawi_glenn

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    read the rules.
     
  6. Oct 21, 2007 #5

    malawi_glenn

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    now you did stuff that are MORE against the rules. the guy who asks MUST show attempt to solution before help is given. And never should whole solutions be given.

    And use edit button if if you want to add more in posts...
     
  7. Oct 21, 2007 #6
    Anyone got any help?

    Not sure what the above is suppose to be going on about:confused:
     
  8. Oct 21, 2007 #7

    malawi_glenn

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    The rules are that you first show work done, and that you have attempted to get a solution etc. The template must be used. And you are not allowed to post the answer and so on if the questioner has not shown work done.
     
  9. Oct 22, 2007 #8
    I understand the logic table of an AND logic gate:

    0+0 = output 0
    0+1 = output 0
    1+0 = output 0
    1+1 = output 1

    But what i don't understand is how i am supposed to draw the diagram as i don't understand what its asking me to draw.
     
  10. Oct 22, 2007 #9

    berkeman

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    Draw a 4-input AND gate. It has 4 inputs and one output, right? And the truth table for the 4-input AND gate is basically like what you have written -- all the inputs must be 1 in order for the output to be a 1, right?

    Now draw the three 2-input AND gates, placed in a vertical line so the inputs are all on the left, and the 3 outputs are on the right. Do you see how the top two 2-input NANDs look sort of like a 4-intput AND, but they have a total of 2 outputs intead of 1? Can you think of a way to use the bottom AND to combine those outputs somehow? Work out the truth tables for different ways of combining the gates, to see if you can match the truth table for the 4-input AND gate.
     
  11. Oct 22, 2007 #10
    Cheers for that, big help :)
     
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