Connect with us


Discussion in 'Electronic Basics' started by Sunil, Oct 11, 2007.

Scroll to continue with content
  1. Sunil

    Sunil Guest

    hi.....can anyone define input and output impedence of a transistor??
    and how do you find it out experimentally??
  2. Eeyore

    Eeyore Guest

    It depends on the circuit it's operated in. If you're referring to the device
    itself alone, those parameters will vary with collector current.

    By measurement !

    Now, maybe you can us about the reason behind your question.

  3. Sunil

    Sunil Guest

    my professor measured it using the ratio between Rin and Rs (internal
    resistance)....i kinda dint understand that...can u xplain me this
  4. Rich Grise

    Rich Grise Guest

    Why can't you go to the prof., and say, "I still don't get this -
    can you explain it to me again, in a form I can understand?"

    Good Luck!
  5. Eeyore

    Eeyore Guest

    Frankly, if you want my precise opinion, most 'professors' haven't the tiniest
    clue about real world electronics and would be better employed cleaning the
    lavatories than teaching kids who actually want to learn something of value.

    I have experienced the same frustration myself (at UCL London would you believe
    ?) but it was solved by a supposedly 'inferior' teacher at a mere polytechnic
    who wrote an excellent series of articles on precisely this subject in the
    reknowned UK magazine "Wireless World". He swept away the usual professor's
    stuffy nonsense and voodoo and replaced it with simple to understand practical

    Now, I don't have a reference for those articles I'm afraid but it seems to me
    that maybe it's time to find out which issues they were in. The approximate time
    frame for this is the mid 1970s.

  6. Eeyore

    Eeyore Guest

    I went to the Prof (age 18) and said (something along the lines of to the best
    of my memory) why are you using Y parameters when no damn * (OK I didn't say
    "damn") semiconductor manufacturer publishes any such damn * thing and I think
    he was mostly embarassed that a student was probably better informed about
    current practice than he was.

    His answer when I suggested that H parameters might be more useful was IIRC
    "that's another way you can do it". DUH !

    What a useless piece of trash ! I had 2 very good friends on the course who both
    admitted at the end of the first year "I still don't understand what a
    transistor does". I did and I hadn't learnt it at UCL and that's why I left.

  7. bg

    bg Guest

    Sunil wrote in message
    Connect a battery and a resistor in series with a base emitter junction.
    Measure the voltage across the resistor and the voltage across the BE
    junction. From ohms law you can figure out the current flowing into the
    junction and the resistance of the junction. The BE junction normally
    operates somewhere between .6 to .7 volts, so keep the BE voltage within
    that range for realistic values. Over that range of BE voltages , you should
    see that the resistance of the junction changes. If it didn't change, it
    would be a simple matter of measuring it with an ohmeter.
    This is something that you should have done and understood using dry cells
    and light bulbs long before getting into transistors.
  8. Eeyore

    Eeyore Guest

    You just measured a DIODE not a transistor.

    Please don't flaunt your ignorance in this way.

  9. bg

    bg Guest

    Ok so we measured h and not Bh, but the flaunting is not negotiable.
  10. Jamie

    Jamie Guest

    Now you're starting to sound like one of the brothers,
    here in the states!.
    Keep it up, you'll be wearing an American patch very soon!
  11. Jamie

    Jamie Guest

    No comment.. How ever, I do admire your truthfulness.

    There is some good there, just damn hard to find.
  12. Jamie

    Jamie Guest

    Pay no mind to Mr Ham.. He can be as rude as he can be ignorant.

    Frankly, I don't understand the instructor placing a question in suck
    an awkward manner? In any case. Your idea of applying current in the base,
    assuming the emitter is at common, is just one step less than that of
    the final process of measuring the current from source to C.(collector).

    This would then give you the current gain ratio. found in reference of
    Hfe, also found in text as Beta.
    Now most of us know, that figure is not absolute due to the nature of
    bipolar transistors.

    The above assumes bipolar, since, that is most likely what they teach
    first in school.
  13. Eeyore

    Eeyore Guest

    Whereas you can be relied upon to be ignorant and WRONG about everything.

  14. Eeyore

    Eeyore Guest

    "Brothers" ? I thought that was a reference to 'black' people.

    Not everything American is a bad thing !

  15. Noway2

    Noway2 Guest

    The book, "The Art of Electronics" does an excellent job of explaining
    how transistors work AND I might add, how to use them in practical
  16. bg

    bg Guest

    Jamie wrote in message ...
    Graham is right. I gave a wrong answere.Unlike some people, I don't have a
    problem with that.
  17. Eeyore

    Eeyore Guest

    I apologise for my bluntness.

  18. Jamie

    Jamie Guest

    Well, you may think so how ever, over here black people call
    white people brothers. That does stir up the pot a bit!
    You change your mind like most people change their underwear.

    Like I said, most people. That may exclude you.!
  19. Jamie

    Jamie Guest

    I understand that how ever, the procedure you describe even though
    wasn't correct, was just incomplete of what should have been done in
    my opinion.

    Many people make mistakes how ever, I find that many of them are not
    due to some one not knowing. They are due to oversight of an error made
    while thinking ahead to fast.

    It's like taking a test.

    A person sets up a pool of questions. This person may just be
    taking references out of a book and only expecting 1 answer..

    In many cases, the person preparing the test is not really savvy
    (hands on) in the field. So in his mind, it's straight forward.

    Along comes the victim taking the test.

    Now, if this victim studied the same reference materials, that of the
    question pool. He's going to know only 1 answer how ever, some one that
    has already been around the barn a few times is going to look at that
    question and come up with multiple scenarios. which in that case, starts
    a flame war here.

    Nothing directed to you, just an observation i've made here lately.

    There are a couple here that change their minds like the wind in New
    England to suite their daily needs.

    Oh well.

    Have a great day,.
  20. Jamie

    Jamie Guest

    That's today.
Ask a Question
Want to reply to this thread or ask your own question?
You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.
Electronics Point Logo
Continue to site
Quote of the day