CHAPTER 19 AMPLIFIERS AND OSCILLATORS 1 Transistor AC

CHAPTER 19 AMPLIFIERS AND OSCILLATORS 1

Transistor AC equivalent circuits l l 2 h (hybrid) parameters r parameters

Relation of transistor symbol to rparameter equivalent 3

The AC bata and Remember that and l 4

COMMON-EMITTER AMPLIFIERS 5

DC equivalent circuit for CE 6 DC equivalent (C-open circuit) AC equivalent (C-short circuit)

r-parameter model 7

A Bypass Capacitor Increases Voltage Gain 8

Phase Inversion and AC input resistance 9

Phase Inversion and AC input resistance l l 10 The CE amplifier, the output voltage at the collector is 180°out of phase with the input voltage at the base The dc input resistance (RIN) can be defined as:

Phase Inversion and AC input resistance l l 11 The CE amplifier, the output voltage at the collector is 180°out of phase with the input voltage at the base The dc input resistance (RIN) can be defined as:

Current and Power gain for CE l Current gain is the source current is calculated by l 12 Power gain

COMMON-COLLECTOR AMPLIFIERS (EMITTER-FOLLOWER) 13

Voltage gain and Input resistance for CC 14

Current and Power gain for CC l Current gain is the source current is calculated by l 15 Power gain

The Darlington Pair 16

COMMON-BASE AMPLIFIERS 17

Voltage and Current gain for CB Voltage gain 18 Current gain

Power gain and Input Resistance Power gain 19 Input resistance

FET Amplifiers l Transconductance of a FET – – 20 The transconductance is one factor that determines the voltage gain of a FET amplifier Sometime called the forward transconductance and is designated with units of Siemens (S(

Common-Source (CS) Amplifiers 21

Voltage gain and Input Resistance for CS 22

Common-Drain (CD) or Source-follower Amplifiers 23

Common-Gate (CG) Amplifiers 24

Voltage gain and Input Resistance Voltage gain 25 Input resistance

MULTISTAGE AMPLIFIERS 26 l Multistage gain l Decibel Voltage Gain

Multistage Analysis 27

Multistage Analysis (continue) l 28 The voltage gain of the first stage is reduced by the loading of the second stage

CLASS OPERATION l l 29 CLASS A OPERATION CLASS B OPERATION CLASS AB OPERATION CLASS C OPERATION

CLASS A OPERATION 30

CLASS A OPERATION) continue( l 31 A noncentered Q-point Limits Output Swing

CLASS B PUSH-PULL AMPLIFIER OPERATION 32

CLASS B PUSH-PULL AMPLIFIER OPERATION) continue( 33

CLASS B PUSH-PULL AMPLIFIER OPERATION) continue( 34

CLASS AB OPERATION 35

CLASS AB OPERATION (continue) 36

CLASS C OPERATION l 37 Class C amplifiers are biased so that conduction occurs for much less than 180°, and are more efficient than either class A or class B

OSCILLATORS l l Oscillator Principles An oscillator converts electrical energy in the form of DC to electrical energy in the form of AC Condition for oscillation – – 38 The phase shift around the feedback loop must be 0° The loop gain must be least 1 (unity gain)

Oscillator Principles (positive feedback) 39

Start-up conditions 40

The RC Oscillator 41

The Colpitts Oscillator 42

The Hartley Oscillator 43

The Clapp Oscillator 44

The crystal oscillator 45

The crystal oscillator (continue) 46