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  1. #1
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    bipolar active linear region

    The bipolar active linear (amplification) region is defined as Vbe>0 and Vbc<0, and the saturation region is defined as Vbe>0, and Vbc>0. Note that this is bipolar, the saturation region of bipolar with similar with the linear region of cmos.

    In my simulation, Vbe=0.75V, I sweep the Vce from 0 to 2V, and I found that the collector current becomes almost constant when Vce is larger than 0.3V. We can say that when Vce is larger than 0.3V, BJT is in active linear region.

    The confusion is that in definition, for the active linear region, the definition requires Vbc<0. However, in my simulation, Vbc=0.7-0.3=0.4V >0, and BJT enters the active linear region. Why? Can you please explain?


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  2. #2
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    Re: bipolar active linear region

    Your definition Vbc<0 is not correct.
    Exact statement should be B-C junction is reverse biased for Linear region,Forward biased for Saturation Region.
    So B-C junction is forward biased whilst the Vbc>0.x V.


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  3. #3
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    Re: bipolar active linear region

    The definition is arbitrary and does not comprehend
    that the "saturation region" is a continuum of declining
    hFE and Rc, both, as Vce approaches zero.

    Check out the relation of "forced beta" to "Vce(sat)"
    and see that current gain persists well into saturation.


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