Lec#2BasicBJTAmplifier UniMAP PortalLEC # 2basicbjtamplifier德艺门.pptVIP

ANALOG ELECTRONIC CIRCUITS 1 EKT 204 Basic BJT Amplifiers (Part 1) * Analog Signals Linear Amplifiers Analog signals Natural analog signals: physical sense (hearing, touch, vision) Electrical analog signals: e.g. output from microphone, output signal from compact disc – form of time-varying currents voltages Magnitude: any value which vary continuously with time Analog circuits Electronic circuits which produce analog signals E.g. linear amplifier Linear amplifier Magnifies input signal produce output signal that is larger directly proportional to input signal DC voltage source Amplifier Load Signal source DC power Low signal power High signal power (a) (b) Block diagram of a compact disc player system * The Bipolar Linear Amplifier To use circuit as an amplifier, transistor needs to be biased with DC voltage at quiescent point (Q-point) ? transistor is biased in forward active region Time-varying output voltage is directly proportional to larger than time-varying input voltage ? linear amplifier (a) Bipolar transistor inverter circuit; (b) inverter transfer characteristics * The Bipolar Linear Amplifier Summary of notation Variable Meaning iB, vBE Total instantaneous values IB, VBE DC values ib, vbe Instantaneous ac values Ib, Vbe Phasor values * Graphical Analysis AC Equivalent Circuit (D) Common-emitter transistor characteristics, dc load line, and sinusoidal variation in base current, collector current, and collector-emitter voltage RC RB vs vO VBB VCC (C) Common-emitter circuit with time varying signal source in series with base dc source iB iC vBE vCE Fig. C Fig. D * Graphical Analysis AC Equivalent Circuit Base on Fig. C D (time-varying signals linearly related superimposed on dc values) If signal source, vs = 0: * Graphical Analysis AC Equivalent Circuit For B-E loop, considering time varying signals: Rearrange: Base on (5), left side of (7) is 0. So: For C-E loop, considering time varying signals: Base on (6), left side of