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Unformatted text preview: Lecture 25 Graphical Analysis Much like the MOSFET amplifiers, the transconductance amounts to the slope of the collector current curve around the DC bias values The BJTs have a much higher transconductance than MOSFETs This is because we are taking a slope off a diode curve Input Resistance If we want to determine the resistance seen by v be we need to first evaluate the total base current: The signal component of this is: If we substitute for the transconductance: The small signal input resistance between the base and emitter is denoted r Finally, replacing g m and using beta to substitute for the collector current: be T C C C B v V I I i i 1 + = = be T C b v V I i 1 = be m b v g i = m b be g i v r = B T I V r = Input Resistance at the Emitter Sometimes our input signal will enter the emitter terminal Thus we need to determine the emitter resistance for a small signal input The total emitter current is: The emitter signal current is:...
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This note was uploaded on 02/13/2012 for the course PHYSICS 16.365 taught by Professor Staff during the Summer '10 term at UMass Lowell.
 Summer '10
 Staff
 Electronics, Current

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