Microelectronics Circuit Analysis and Design Donald A. Neamen Chapter 8 Output Stages and Power Amplifiers In this chapter, we will: Describe the characteristics of BJT and MOSFET power transistors Define the various classes of power amplifiers and determine the maximum power efficiency of each class of amplifier. class-a power amplifiers. class-ab power amplifiers. Design an output stage using power MOSFETs as the output devices. Neamen Microelectronics, 4e Chapter 8-1 Neamen Microelectronics, 4e Chapter 8-2 Power Amps Interdigitated BJT: Top and Cross-Sectional Views Need larger emitters for power amps. Designed differently. Neamen Microelectronics, 4e Chapter 8-3 Neamen Microelectronics, 4e Chapter 8-4 1
High-Power MOSFET Structures Power Amps VMOS DMOS HEXMOS Neamen Microelectronics, 4e Chapter 8-5 Neamen Microelectronics, 4e Chapter 8-6 Typical dc Beta for 2N3055 Power Amps have smaller B Neamen Microelectronics, 4e Chapter 8-7 Neamen Microelectronics, 4e Chapter 8-8 2
Typical Characteristics for High-Power MOSFET Drain-to-Source Resistance Versus I D Neamen Microelectronics, 4e Chapter 8-9 Neamen Microelectronics, 4e Chapter 8-10 2 Packaging Schemes and Typical Heat Sink Safe Operating Area for BJT Neamen Microelectronics, 4e Chapter 8-11 Neamen Microelectronics, 4e Chapter 8-12 3
Safe Operating Area for BJT Neamen Microelectronics, 4e Chapter 8-13 Neamen Microelectronics, 4e Chapter 8-14 Amplifier Classes I C Versus Time Characteristics class-a class-b class-ab class-c Neamen Microelectronics, 4e Chapter 8-15 Neamen Microelectronics, 4e Chapter 8-16 4
Class-A Common-Emitter Amplifier Class-A CE Amplifier η(max) 25% Neamen Microelectronics, 4e Chapter 8-17 Neamen Microelectronics, 4e Chapter 8-18 Class-A CE Amplifier Class-A CE Amplifier Example.. Neamen Microelectronics, 4e Chapter 8-19 Neamen Microelectronics, 4e Chapter 8-20 5
Class-B Complementary Push-Pull Output Stage Voltage Transfer Characteristics: Complementary Push-Pull Output Stage dead band Neamen Microelectronics, 4e Chapter 8-21 Neamen Microelectronics, 4e Chapter 8-22 Crossover Distortion: Complementary Push-Pull Output Stage Effective Load Line: Ideal Class-B Output Stage Crossover Distortion Neamen Microelectronics, 4e Chapter 8-23 Neamen Microelectronics, 4e Chapter 8-24 6
Ideal Class-B Output Stage Ideal Class-B Output Stage Neamen Microelectronics, 4e Chapter 8-25 Neamen Microelectronics, 4e Chapter 8-26 Ideal Class-B Output Stage Average Power Dissipation Versus Peak Output Voltage: Class-B Output Stage 2 VCC PQn (max) = 2 π R η(max) 78.5% L Neamen Microelectronics, 4e Chapter 8-27 Neamen Microelectronics, 4e Chapter 8-28 7
Bipolar Class-AB Output Stage BJT Class-AB Output Stage Neamen Microelectronics, 4e Chapter 8-29 Neamen Microelectronics, 4e Chapter 8-30 BJT Class-AB Output Stage Characteristics of Class-AB Output Stage Neamen Microelectronics, 4e Chapter 8-31 Neamen Microelectronics, 4e Chapter 8-32 8
MOSFET Class-AB Output Stage MOSFET Class-AB Output Stage Neamen Microelectronics, 4e Chapter 8-33 Neamen Microelectronics, 4e Chapter 8-34 MOSFET Class-AB Output Stage Effective AC Load Line: Class-C Amplifier Neamen Microelectronics, 4e Chapter 8-35 Neamen Microelectronics, 4e Chapter 8-36 9
Inductively Coupled Class-A Amplifier Transformer-Coupled Common Emitter Neamen Microelectronics, 4e Chapter 8-37 Neamen Microelectronics, 4e Chapter 8-38 Transformer-Coupled Emitter Follower Class-AB Output Stage: Q-Point Established by Diodes Neamen Microelectronics, 4e Chapter 8-39 Neamen Microelectronics, 4e Chapter 8-40 10
Class-AB Output Stage: V BE Multiplier Bias Class-AB Output Stage: Input Buffer BJTs Neamen Microelectronics, 4e Chapter 8-41 Neamen Microelectronics, 4e Chapter 8-42 Class-AB Output Stage: Darlington Pair Neamen Microelectronics, 4e Chapter 8-43 11