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university:courses:electronics:text:chapter-10 [21 Sep 2013 16:59] – created Doug Merceruniversity:courses:electronics:text:chapter-10 [12 Aug 2021 00:30] (current) – The symbol for inf Loknath Bharti
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 <WRAP centeralign > Figure 10.1 Two stage cascade amplifier </WRAP> <WRAP centeralign > Figure 10.1 Two stage cascade amplifier </WRAP>
  
-It is necessary to consider what happens when non-ideal amplifiers are put in series. Looking at the example in figure 10.1, it is clear that the input and output resistances (or impedances) come into play by reducing the overall gain. If the amplifiers were ideal (R<sub>out</sub> = 0 and R<sub>in</sub> = 8), and amplifier stages #1 and #2 had gains of A<sub>1</sub> and A<sub>2</sub>, the overall gain would simply be A<sub>1</sub>*A<sub>2</sub>. For the above example, let us now calculate the gain assuming nothing about the R<sub>in</sub> and R<sub>out</sub> of each stage, treating them as voltage dividers between the two stages and between the last stage and the output load. Note that in practice, impedances, Z<sub>in</sub>, Z<sub>out</sub>, would normally be used, not resistances, but the simple resistance will serve to illustrate the point here.+It is necessary to consider what happens when non-ideal amplifiers are put in series. Looking at the example in figure 10.1, it is clear that the input and output resistances (or impedances) come into play by reducing the overall gain. If the amplifiers were ideal (R<sub>out</sub> = 0 and R<sub>in</sub> = ∞), and amplifier stages #1 and #2 had gains of A<sub>1</sub> and A<sub>2</sub>, the overall gain would simply be A<sub>1</sub>*A<sub>2</sub>. For the above example, let us now calculate the gain assuming nothing about the R<sub>in</sub> and R<sub>out</sub> of each stage, treating them as voltage dividers between the two stages and between the last stage and the output load. Note that in practice, impedances, Z<sub>in</sub>, Z<sub>out</sub>, would normally be used, not resistances, but the simple resistance will serve to illustrate the point here.
  
 <WRAP indent > First amplification stage with loss between stage #1 and #2: </WRAP> <WRAP indent > First amplification stage with loss between stage #1 and #2: </WRAP>
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 In this respect consider further the implication that each stage gain depends largely on the ratio of the collector resistance to the (un bypassed) emitter resistance. In this respect consider further the implication that each stage gain depends largely on the ratio of the collector resistance to the (un bypassed) emitter resistance.
  
-Respond critically to the suggestion of obtaining an order of magnitude increase in gain by a factor of ten increase in the collector resistance. +<note warning>This section may be incomplete due to lack of interest.</note>
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-Similarly respond critically to the alternative suggestion of obtaining an order of magnitude increase in gain by decreasing the un bypassed emitter resistance by a factor of ten. +
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-{{ :university:courses:electronics:text:chptr10_f7.png?500 |}} +
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-<WRAP centeralign > Figure 10.2.2. Adding negative feedback </WRAP> +
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-{{ :university:courses:electronics:text:chptr10_f8.png?500 |}} +
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-<WRAP centeralign > Figure 10.2.3.  </WRAP> +
 =====10.3 The Cascode===== =====10.3 The Cascode=====
  
university/courses/electronics/text/chapter-10.1379775557.txt.gz · Last modified: 21 Sep 2013 16:59 by Doug Mercer

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