Lecture17-BJT+Small+Signal+Model+2

# Lecture17-BJT+Small+Signal+Model+2 - ECE 3040:...

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ECE 3040 - Dr. Ying Zhang Georgia Tech ECE 3040: Microelectronic Circuits Lecture 17 Reading: Jaeger 13.5-13.6, Notes

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ECE 3040 - Dr. Ying Zhang Georgia Tech Recapture BJT Small Signal Model: Hybrid-Pi Model C CE A o m o C T o C T C m I V V y r g I V y r I V I y g + = = = = = = = 22 11 21 1 1 40 ββ π Transconductance Input Resistance Output Resistance Y-parameter Model Hybrid-pi Model v 1
ECE 3040 - Dr. Ying Zhang Georgia Tech Voltage Controlled Current source version of Hybrid-pi Model Current Controlled Current source version of Hybrid-pi Model b o b m be m i i r g v g β π = = Recapture BJT Small Signal Model: Hybrid-Pi Model ( Alternative Representations)

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ECE 3040 - Dr. Ying Zhang Georgia Tech ± Single Transistor Amplifier Analysis ± BJT Base Charging Capacitance ± BJT Depletion Capacitance ± Complete BJT Small-Signal Model Agenda
ECE 3040 - Dr. Ying Zhang Georgia Tech Single Transistor Amplifier Analysis 1.) Determine DC operating point and calculate small signal parameters (see next page) 2.) Convert to the AC only model. DC Voltage sources are shorts to ground DC Current sources are open circuits Large capacitors are short circuits Large inductors are open circuits 3.) Use a Thevenin circuit (sometimes a Norton) where necessary. Ideally the base should be a single resistor + a single source. Do not confuse this with the DC Thevenin you did in step 1. 4.) Replace transistor with small signal model 5.) Simplify the circuit as much as necessary. Steps to Analyze a Transistor Amplifier Step 2 Step 3 Step 4 Step 5 Step 1 Important! 6.) Calculate the small signal parameters (r π , g m , r o etc…) and then gains etc…

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ECE 3040 - Dr. Ying Zhang Georgia Tech BJT Base Charging Capacitance (Diffusion Capacitance) + = = 0 0 ' 1
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## This note was uploaded on 09/05/2009 for the course ECE 3040 taught by Professor Hamblen during the Spring '07 term at Georgia Institute of Technology.

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Lecture17-BJT+Small+Signal+Model+2 - ECE 3040:...

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