DMT 2313 Electronic II Lecture IV Basic BJT

DMT 231/3 Electronic II Lecture IV Basic BJT Amplifiers III WEEK III SEM I 2007/08

COMMON-COLLECTOR AMPLIFIER q SMALL-SIGNAL VOLTAGE GAIN q INPUT AND OUTPUT IMPEDANCES q SMALL-SIGNAL CURRENT GAIN WEEK III SEM I 2007/08 2

COMMON-COLLECTOR AMPLIFIER Circuit v. O Emitter-follower circuit WEEK III SEM I 2007/08 Small-signal equivalent circuit 3

COMMON-COLLECTOR AMPLIFIER Small Signal Analysis: Voltage Gain, Impedance Another small-signal equivalent circuit WEEK III SEM I 2007/08 4

COMMON-COLLECTOR AMPLIFIER Small Signal Analysis: Current Gain Current gain where If R 1 R 2 Rib & ro RE then Ai (1+ ) WEEK III SEM I 2007/08 5

COMMON-BASE AMPLIFIER q SMALL-SIGNAL VOLTAGE GAIN q INPUT AND OUTPUT IMPEDANCES q SMALL-SIGNAL CURRENT GAIN WEEK III SEM I 2007/08 6

COMMON-BASE AMPLIFIER Circuits Common-base circuit Small-signal equivalent circuit WEEK III SEM I 2007/08 7

COMMON-BASE AMPLIFIER Small Signal Analysis: Voltage & Current Gain Voltage gain If RS approaches zero, then Av = gm(RC||RL) Current gain If RE approaches infinity and RL approaches zero, then short-circuit current gain WEEK III SEM I 2007/08 8

COMMON-BASE AMPLIFIER Small Signal Analysis: Impedance Input resistance Rie Ii Ib Ri = re = WEEK III SEM I 2007/08 9

COMMON-BASE AMPLIFIER Small Signal Analysis: Impedance Output resistance Ro Ix Vx Ro = R C WEEK III SEM I 2007/08 10

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