How to measure I-V family with a curve tracer or o-scope

Discussion in 'The Projects Forum' started by globtrotah, May 13, 2008.

  1. globtrotah

    Thread Starter New Member

    May 12, 2008
    2
    0
    Hi,
    I've been trying to measure several characteristics of an NMOS without success. I need to know how to use a curve tracer or o-scope (using electronics workbench and the real equipment) to make the following measurements: I-V family
    Threshold
    Transconductance curve
    Pinch off voltage
    Gm(gain)

    I also need to obtain the following measurements using a BJT: Diode curve, Base turn on voltage, I-V characteristics, early voltage and beta(gain).

    I'm really confused about how to do this, I believe in each case i'm supposed to connect the transistor in series with a resistor and then take the readings but i'm not getting any results. I'm not really sure how to set up the circuit and equipment to get these readings. Someone please help!
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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  3. globtrotah

    Thread Starter New Member

    May 12, 2008
    2
    0
    Thanks a lot for the link. Please could you show me the circuit configuration needed for the extraction of NMOS parameters? I have tried several configurations (I've also searched the web for hours) but all I keep getting is an overload indication on the power source.
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    I've not used such a device in the last 20 years. My experience was all in BJT stuff.

    Remember that NMOS is voltage rather than current controlled, and that the gate voltage should never go higher than 10 volts relative to the source. These are not power devices, so use a realistic voltage and resistor on the drain.
     
  5. n9352527

    AAC Fanatic!

    Oct 14, 2005
    1,198
    4
    Is your curve tracer a Tek? Which model?

    I'll try to dig up my notes on FET and BJT parameters extractions, it had been 13 years since I did my last characterisations so I don't remember all the details. However, I remember I didn't use any series resistor at all. The tracer limits the current (or voltage) depending on the maximum power setting, and keeps the DUT from overheating through pulse measurements (usually 300us or 80us pulses).
     
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