3-Handouts_Handout_3c - Signal Injection and Extraction ¡...

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Unformatted text preview: Signal Injection and Extraction ¡ In forward-active region, ¡ To cause change in current, v BE = v B- v E must be changed. Base or emitter terminals are used to inject signal because even if Early voltage is considered, collector voltage has negligible effect on terminal currents. ¡ Substantial changes in collector or emitter currents can create large voltage drops across collector and emitter resistors and collector or emitter can be used to extract output. Since i B is a factor of β smaller than i C or i E currents, base terminal is not used to extract output. ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ = = T V BE v S I E i T V BE v S I C i exp exp α ⎟ ⎟ ⎟ ⎟ ⎠ ⎞ ⎜ ⎜ ⎜ ⎜ ⎝ ⎛ = T V BE v S I B i exp β Amplifier Families ¡ Constraints for signal injection and extraction yield three families of amplifiers ¡ Common-Emitter (C-E) ¡ Common-Base (C-B) ¡ Common-Collector (C-C) ¡ Coupling and bypass capacitors are used to change the ac equivalent circuits and to keep the operating point constant when cascading amplifier stages Inverting Amplifiers: Common-Emitter For the common-emitter amplifier shown assume r π =10k Ω, r o =220k Ω , and β =100. Calculate: v o /v b ?...
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3-Handouts_Handout_3c - Signal Injection and Extraction ¡...

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