网络电视业务实现方案研究 - 上海交通大学.pptVIP

Chapter 9 output stages and power amplifiers Power Amplifier Small-signal approximation and models either are not applicable or must be used with care. THD (total harmonic distortion) Deliver the power to the load in efficient manner. Ex. To provide the amplifier with a low output resistance so that it can deliver the output signal to the load without loss of gain. Power dissipation is as low as possible. Classification of Power Amplifier Power amplifiers are classified according to the collector current waveform that results when an input signal is applied. Conducting angle. Classification of Power Amplifier Classification of Power Amplifier CE amplifier is not proper for using as a power amplifier Class A Output Stage Class A Output Stage Class B Output Stage Class B Output Stage Transfer Characteristic Crossover Distortion Power –conversion efficiency The load power Maximum load power Power –conversion efficiency Total supply power Maximum total supply power Power –conversion efficiency Power-conversion efficiency Maximum power-conversion efficiency Power Dissipation Power dissipation Maximum Power dissipation Power Dissipation At the point of maximum power dissipation the efficiency can be evaluated: Example: 9.1 Reducing crossover distortion Class AB Output Stage A Class AB Output Stage Utilizing Diodes for Biasing A Class AB Output Stage Utilizing A VBE Multiplier for Biasing Homework: May 25th, 2008 9.12; 9.13; 9.14; 9.15 SJTU Yang Hua Microelectronic Circuits Microelectronic Circuits SJTU Yang Hua Introduction 9.1 Classification of output stages 9.2 Class A output stage 9.3 Class B output stage 9.4 Class AB output stage 9.5 Biasing the class AB circuit Collector current waveforms for transistors operating in (a) class A, (b) class B class AB class C DC supply power: ICQVcc , the area of ABCO Rc power: ICQURc， the area of QBCD Collector dissipation power: ICQUCEQ， the area of AQDO Load power: Figure