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  • Transistor: active or saturated mode

    Pranjali Desai

    Member

    Updated: Oct 26, 2024
    Views: 2.3K
    hi....
    when we say that a transistor is in active or in saturated mode;
    what is the practical (physical) meaning behind ?
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Replies

  • ashutoshglamour

    Member • Jul 2, 2009

    transistor is in active mode that means it is used as amplifier.
    when it is in saturation mode it is used as switch.😁
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  • Harshad Italiya

    Member • Jul 2, 2009

    If your Emitter-Base Junction is Forward Bias and Collector-Base junction is Reverse Bias Then your Transistor works in Active State.

    While your Emitter-Base Junction is Forward Bias and Collector-Base Junction is also in Forward Bias Then your Transistor works in Saturation Mode.

    While your Emitter-Base Junction is Reverse Bias and Collector-Base Junction is also in Reverse Bias Then your Transistor works in Cut-off Mode.

    Internal Working:
    in Active State it works as a Amplifier. (as said by Ashutosh)

    While in Saturation State: Here both EB and CB junctions are in forward bias so there is a large value of current available and you can use transistor as a CLOSE switch.

    and in Cutoff state:both EB and CB junctions are in Reverse bias so there is no flow of current through transistor and in this case you can use transistor as a OPEN switch.

    PS: Apply simple PN junction rule at the both junction you will get the answer why there is Large current and why there is no current flow in saturation and Cutoff State.

    Here is the Characteristics of transistor : #-Link-Snipped-#
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  • mithunganesh

    Member • Jul 6, 2009

    Sine wave formula

    Sine wave formula is
    128+128sin(degrees)
    is also correct friend,,
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  • skipper

    Member • Jul 6, 2009

    A transistor is a bimodular device; the charge 'flowing" across the junction is set by the width of a diffusion layer. The reverse (or forward) bias effectively pinches the flow off (or lets it through).

    In that sense a FET or a bipolar junction device is a kind of valve; setting the valve is like governing an engine, which is why amps have feedback to do this and keep the circuit out of saturated mode.
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  • Pranjali Desai

    Member • Jul 14, 2009

    thak you all!!and specially godfather.
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  • Harshad Italiya

    Member • Jul 14, 2009

    Pranjali Desai
    thak you all!!and specially godfather.
    Welcome PD!
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  • Munguti

    Member • Jul 30, 2009

    The important thing is to know were the Q point lies in the load line, we have the cut-off, active and saturated point all corresponding to the off, amplifier mode and on mode of a transistor respectively.
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