Lecture21-BJT ExamplesAndPspiceSim

Lecture21-BJT ExamplesAndPspiceSim - ECE 3040 - Dr. Alan...

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Unformatted text preview: ECE 3040 - Dr. Alan Doolittle Georgia Tech Lecture 21 Bipolar Junction Transistors (BJT): Part 5 Hand Example, SPICE Example, and Limits on output swing imposed by having to stay within Forward Active Mode Reading: Notes ECE 3040 - Dr. Alan Doolittle Georgia Tech An Example that puts it all together! Consider an Integrated Circuit npn BJT with: Emitter Doping, N DE =7.5e18 cm-3 Base Doping, N AB =10e17 cm-3 Collector Doping, N DC =1.5e16cm-3 Substrate doping N Sub = 5e15 cm-3 Minority Carrier Diffusion coefficient in the emitter, D pE-(holes) = 5 cm 2 /s Minority Carrier Diffusion coefficient in the base, D nB-(electrons) = 10 cm 2 /s Base Quasi-neutral width, W = 300 nm Minority Carrier Diffusion length in the emitter, L E = 250 nm Minority Carrier Diffusion length in the base, L B = 100 um Areas: A emitter-base = 25 um 2 , A collector-Base = 100 um 2 , A substrate-Collector = 500 um 2 Resistances and Early Voltage: r b = 250 , r c = 200 , r ex = 5 , V A = 35 V Find the complete small- signal model for: I C =100 mA, V CE =2V, and V CS =2V and V be =0.5V bi For the emitter-base ECE 3040 - Dr. Alan Doolittle Georgia Tech An Example that puts it all together! First recognize that W<<L B so we can use the simplest form of the transport parameters. Next, recognize that our choice of generic labeling allows us to use the equations developed for the pnp transistor here even though you were given a npn transistor....
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Lecture21-BJT ExamplesAndPspiceSim - ECE 3040 - Dr. Alan...

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