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Transistors acting as resistors

  1. Mar 8, 2013 #1
    From what I understand, transistors can be viewed as several things, one of which is a resistor.

    So how much resistance is a transistor turned on generally equivalent to?

    And what is normally considered a large or small resistance? I know voltmeters have a large internal resistance in the order of megaohms. And I believe transistors are in the order of kilos, so would transistors acting as resistors be considered as having a low resistance?
  2. jcsd
  3. Mar 8, 2013 #2
    Some bipolar transistors, when turned fully on, will have a voltage drop across the collector and emitter of approximately 0.3 volts (silicon based).

    For MOSFET's, when turned fully on, there is a on-resistance in the order of milliohms. I would suggest looking at the datasheet for the transistor using.

    If you are using the small-signal model of a transistor then you will be able to describe it as resistors and controlled current/voltage sources.
  4. Mar 8, 2013 #3


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    Certain MOSFETS are used a voltage-controlled variable resistors. Google "Siliconix VCR"
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