Lecture 11_ Feb 11 2011

# Lecture 11_ Feb 11 2011 - Chapter 13 Small-Signal Modeling...

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Unformatted text preview: Chapter 13 Small-Signal Modeling and Linear Amplification Lecture 11 Covered Sections: 13.2, 13.6, 13.7 Common – Emitter Amplifier Coupling and Bypass Capacitors • AC coupling through capacitors is used to inject ac input signal and extract output signal without disturbing Q-point • Capacitors provide negligible impedance at frequencies of interest and provide open circuits at dc. C 1 and C 3 are large-valued coupling capacitors or dc blocking capacitors whose reactance at the signal frequency is designed to be negligible. C 2 is a bypass capacitor that provides a low impedance path for ac current from emitter to ground, thereby removing R E (required for good Q-point stability) from the circuit when ac signals are considered. Chap 13.2 dc and ac Analysis • DC analysis: – Find dc equivalent circuit by replacing all capacitors by open circuits and inductors by short circuits. – Find Q-point from dc equivalent circuit by using appropriate large- signal transistor model. • AC analysis: – Find ac equivalent circuit by replacing all capacitors by short circuits, inductors by open circuits, dc voltage sources by ground connections and dc current sources by open circuits. – Replace transistor by small-signal model – Use small-signal ac equivalent to analyze ac characteristics of amplifier....
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## This note was uploaded on 03/06/2011 for the course ECE 255 taught by Professor Staff during the Spring '08 term at Purdue.

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Lecture 11_ Feb 11 2011 - Chapter 13 Small-Signal Modeling...

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