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university:courses:electronics:text:chapter-9 [21 Sep 2016 03:10] – change 3 to 5 Doug Merceruniversity:courses:electronics:text:chapter-9 [26 Feb 2017 13:48] – [9.7.2 BJT Version DC Biasing techniques] Jack Liu
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   -  In this circuit, to keep I<sub>c</sub> independent of β, the following condition must be met:   -  In this circuit, to keep I<sub>c</sub> independent of β, the following condition must be met:
  
-<m> I_c = βI_b = ( βV_+ - B_BE ) / (R_L +(β+1)R_L) approx (V_+ - V_BE)/R_L </m>+<m> I_c = βI_b = (βV_+ - βB_BE ) / (R_F +(β+1)R_L) approx (V_+ - V_BE)/R_L </m>
  
 which is the case when: which is the case when:
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 The input source resistance R<sub>S</sub> and the equivalent resistance at the base, R<sub>base</sub> form a voltage divider. To calculate the overall voltage gain from voltage source V<sub>in</sub> to V<sub>out</sub> we multiply this divider ratio times the base to collector gain, A<sub>V</sub> we just calculated. The input source resistance R<sub>S</sub> and the equivalent resistance at the base, R<sub>base</sub> form a voltage divider. To calculate the overall voltage gain from voltage source V<sub>in</sub> to V<sub>out</sub> we multiply this divider ratio times the base to collector gain, A<sub>V</sub> we just calculated.
  
-<m> R_base / (R_S + R_base ) A_V = 392.5/10392.5 * 148 = 5.6 </m>+<m> R_base / (R_S + R_base ) A_V = (392.5/10392.5) * 148 = 5.6 </m>
  
 From our investigation of the inverting op amp configuration in Chapter 3 we learned that for amplifiers with less than infinite gain the actual gain will be less than the ideal gain equation, Gain = -R<sub>F</sub>/R<sub>S</sub> predicts. If our single transistor amplifier had infinite gain the gain from V<sub>in</sub> to V<sub>out</sub> would be 62.7KΩ/10KΩ or 6.27. In Chapter 3 we got an estimation of the percentage error, ε, due to finite gain A<sub>V</sub> (remember β in this equation is the feedback factor not the current gain of the transistor): From our investigation of the inverting op amp configuration in Chapter 3 we learned that for amplifiers with less than infinite gain the actual gain will be less than the ideal gain equation, Gain = -R<sub>F</sub>/R<sub>S</sub> predicts. If our single transistor amplifier had infinite gain the gain from V<sub>in</sub> to V<sub>out</sub> would be 62.7KΩ/10KΩ or 6.27. In Chapter 3 we got an estimation of the percentage error, ε, due to finite gain A<sub>V</sub> (remember β in this equation is the feedback factor not the current gain of the transistor):
university/courses/electronics/text/chapter-9.txt · Last modified: 07 Oct 2020 16:37 by Doug Mercer

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