Class A , Class B And Class AB Amplifiers Full Details
Introduction Class A Amplifiers offer a very good linearity of the output, meaning that the signal is faithfully reproduced, however their efficiency is very low, around 20-30 % in most of the cases. On the other hand, Class B Amplifiers present a very high efficiency up to 78.5 % but cannot reproduce the output faithfully. Indeed, a crossover distortion appears in a push-pull configuration and the use of a negative feedback is required to limit this effect. In order to combine both the excellent linearity of class A and the high efficiency of class B, the class AB has been developed. In the very first section, we will present the general functioning and characteristics of class AB amplifiers. Thereafter, we will discuss the efficiency of class AB configurations. The following section will present some possible biasing methods and we will highlight that the diode biasing is the most appropriate. Finally we will see that even the dio...