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active & passive device

Discussion in 'Electrical Engineering' started by Te-Jung Lo, Jun 28, 2003.

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  1. Te-Jung Lo

    Te-Jung Lo Guest

    Why inductor, capacitor and resistor are called passive device, while
    transistor, diode and FET are call active device!!

    any response will be highly appreciated!
  2. Gym Bob

    Gym Bob Guest

    A diode is not an active device. It does not perform any active function.
  3. Dave M.

    Dave M. Guest


    Transistors and FET's require a source of energy for thier operation and
    have outputs that are a function of input signals.

    Resistors, capacitors, inductors and diodes are devices that do not require
    a source of energy for thier operation.

    Dave M.
  4. The distinction between passive and active devices is not always that

    Consider a tunnel diode or certain thermionic diodes. Under certain
    conditions, they can be turned into oscillators. What about an SCR? Once
    turned on it is about as active as any other switch. Even passive componets
    such as resistors and inductor do their work only if supplied with power.

  5. When a diode is considered "inactive", does that make it a passive device?
    If that were the case, would that not mean that every xsistor when turned
    off becomes a passive device?

    Passive devices are things such as coils, resistor, capacitors. I have never
    personally heard of anyone calling a diode passive.
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