Class-B Audio Amplifier Design With Feedforward Output Stage
AN IMPROVED 'CLASS-B' DESIGN: A simple modification to a standard class-B amplifier dramatically reduces crossover distortion and avoids the need for exact setting of quiescent current. Also published in Electronics World, April 1998, with the title 'Class-B in a new class'. A few people have suggested that 'class-B' is the wrong description, which is why Electronics World changed the title from my original 'improved class-B'. Maybe 'class A+AB' would be more accurate, but misleading, suggesting that high quiescent current is necessary, when in the first version shown next just 15mA was sufficient for a worthwhile improvement.
Distortion Test. Circuit Design.
Improved Version. A new improved version of the original design with detailed measurement and simulation results. The almost complete elimination of crossover distortion is a feature of this design, but stability is not as easily predictable as for my mosfet designs, and so this is recommended only for experienced constructors. A simplified circuit can be found here which is what this design started from.
Output Stage Variations.
A few additional output stage variations. There are many other variations, but these avoid the need for quiescent current adjustment.