series-aiding effect

Discussion in 'General Electronics Chat' started by vustudent, Feb 27, 2010.

  1. vustudent

    Thread Starter Active Member

    Mar 11, 2009
    38
    0
    http://www.allaboutcircuits.com/vol_3/chpt_4/7.html

    Notice in Figure above that the output voltage goes from practically nothing (cutoff) to 15.75 volts (saturation) with the input voltage being swept over a range of 0.6 volts to 1.2 volts. In fact, the output voltage plot doesn't show a rise until about 0.7 volts at the input, and cuts off (flattens) at about 1.12 volts input. This represents a rather large voltage gain with an output voltage span of 15.75 volts and an input voltage span of only 0.42 volts: a gain ratio of 37.5, or 31.48 dB. Notice also how the output voltage (measured across Rload) actually exceeds the power supply (15 volts) at saturation, due to the series-aiding effect of the input voltage source.


    what is the series-aiding effect about?
     
  2. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Keep in mind that the collector voltage of a saturated transistor typically goes below the base voltage. That explains this voltage difference being slightly greater than the positive power supply.

    hgmjr
     
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