|
| Class "B" |
| Class B topology uses two output
devices, one to source current and the other to sink current, Each
half of the amplifier operates in linear region for slightly less
than 180° of the AC input waveform, to generate audio in both
directions, NPN &PNP transistors acts as linear switches for
positive and negative going signal voltages |
| Advantages |
| No Bias current. Since NPN and PNP
output transistors alternate (On to Off) there is no sink current.
Efficiency is approximately 60%. |
| Disadvantages |
| The output devices alternate from
positive to negative, but there is no bias applied, therefore high
distortion called "Crossover distortion" is generated
(this is addressed in Class A/B by means of biasing the output
devices) |
| Conclusions and
comments |
| Class B only applies to low cost
designs where high distortion is not objectionable and it is the
most popular design on TTL circuits |
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