head2right Unfortunately the output signal produced by the microphone is

Head2right unfortunately the output signal produced

This preview shows page 14 - 29 out of 104 pages.

head2right Unfortunately, the output signal produced by the microphone is shorted to the power supply.
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Biasing with Base Resistor B BE CC C B BE CC B R V V I R V V I - = - = β , CH5 Bipolar Amplifiers 183 head2right Assuming a constant value for V BE , one can solve for both I B and I C and determine the terminal voltages of the transistor. head2right However, bias point is sensitive to β variations.
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Improved Biasing: Resistive Divider 2 1 2 CC X V R V R R R V + = CH5 Bipolar Amplifiers 184 head2right Using resistor divider to set V BE , it is possible to produce an I C that is relatively independent of β if base current is small. ) exp( 2 1 2 T CC S C V R R I I + =
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Accounting for Base Current CH5 Bipolar Amplifiers 185 head2right With proper ratio of R 1 and R 2 , I C can be insensitive to β ; however, its exponential dependence on resistor deviations makes it less useful. - = T Thev B Thev S C V R I V I I exp
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Emitter Degeneration Biasing CH5 Bipolar Amplifiers 186 head2right The presence of R E helps to absorb the error in V X so V BE stays relatively constant. head2right This bias technique is less sensitive to β (I 1 >> I B ) and V BE variations.
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Design Procedure head2right Choose an I C to provide the necessary small signal parameters, g m , r π , etc. 187 head2right Considering the variations of R 1 , R 2 , and V BE , choose a value for V RE. head2right With V RE chosen, and V BE calculated, V x can be determined. head2right Select R 1 and R 2 to provide V x.
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Self-Biasing Technique CH5 Bipolar Amplifiers 188 head2right This bias technique utilizes the collector voltage to provide the necessary V x and I B . head2right One important characteristic of this technique is that collector has a higher potential than the base, thus guaranteeing active operation of the transistor.
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Self-Biasing Design Guidelines B C V V V R R - << Δ >> β ) 2 ( ) 1 ( CH5 Bipolar Amplifiers 189 head2right (1) provides insensitivity to β . head2right (2) provides insensitivity to variation in V BE . BE CC BE
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Summary of Biasing Techniques CH5 Bipolar Amplifiers 190
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PNP Biasing Techniques CH5 Bipolar Amplifiers 191 head2right Same principles that apply to NPN biasing also apply to PNP biasing with only polarity modifications.
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Possible Bipolar Amplifier Topologies CH5 Bipolar Amplifiers 192 head2right Three possible ways to apply an input to an amplifier and three possible ways to sense its output. head2right However, in reality only three of six input/output combinations are useful.
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Study of Common-Emitter Topology head2right Analysis of CE Core Inclusion of Early Effect head2right Emitter Degeneration 193 Inclusion of Early Effect head2right CE Stage with Biasing
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Common-Emitter Topology CH5 Bipolar Amplifiers 194
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Small Signal of CE Amplifier CH5 Bipolar Amplifiers 195 C m v in m m C out in out v R g A v g v g R v v v A - = = = - = π
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Limitation on CE Voltage Gain R I V V V - CH5 Bipolar Amplifiers 196 head2right Since g m can be written as I C /V T , the CE voltage gain can be written as the ratio of V RC and V T.
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  • Fall '09
  • Amplifier, Volt, Input impedance, Electronic amplifier, Electrical impedance, Buffer amplifier, Bipolar Amplifiers

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