Chapter 9 output stages and power amplifiers . 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.
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Chapter 9 output stages and power amplifiers
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
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.
Power amplifiers are classified according to the collector current waveform that results when an input signal is applied.
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 ofQBCD
Collector dissipation power:ICQUCEQ， the area ofAQDO
Figure 14.3 Transfer characteristic of the emitter follower. This linear characteristic is obtained by neglecting the change in vBE1 with iL. The maximum positive output is determined by the saturation of Q1. In the negative direction, the limit of the linear region is determined either by Q1 turning off or by Q2 saturating, depending on the values of I and RL.
Figure 14.4 Maximum signal waveforms in the class A output stage of Fig. 14.2 under the condition I = VCC /RL or, equivalently, RL = VCC /I.
The load power
Maximum load power
Maximum power-conversion efficiency
Maximum Power dissipation
The diode biasing has an
Thermal stabilization of
May 25th, 2008
9.12; 9.13; 9.14; 9.15