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What is the drawback of Class B power amplifier How is it overcome?
This is major limitation of class B power amplifier. This limitation can be overcome by applying some small forward voltage to each transistor to increase the cut-in voltage. Due to this the Q point gets shifted above X-axis and the operation is no more class B one but it is class “AB” operation.
What is class B biasing?
Class B operation is an amplifier biased so that only half of the input waveform gets reproduced: either the positive half or the negative half. The transistor spends half its time in the active mode and half its time cutoff.
Why Class B biasing would be more suitable for an audio power amplifier?
In amplifiers using class B bias, illustrated in Fig. 5.3. 1, there is no standing bias current (the quiescent current is zero) and therefore the transistor conducts for only half of each cycle of the signal waveform. This dramatically increases efficiency, compared with class A.
What is the conduction angle of class B push pull amplifier?
180 degrees
An ideal Class B amplifier has a conduction angle of 180 degrees, or one half-cycle of a sine wave. This type of amplifier therefore requires two amplifying elements to produce a full sine wave at its output.
Is there a base bias in a Class B amplifier?
Actually the class B amplifier doesn’t has a base bias. The bias occurs at AB class. But you can bias the base in many ways. If you’re using an op amp just like in the image, you could just use feedback. It makes the output equals to the input, just like a buffer but with a power stage.
How to avoid crossover distortion in Class B amplifiers?
Crossover distortion is more of a problem in low and medium power class B amplifiers and the method used to eliminate it, is to use a class B amplifier that has some bias (and quiescent current) added so that the output transistors are conducting continually, and so avoiding the ‘dead zone’ of class B.
What is the efficiency of an AB amplifier?
The formula of the efficiency (η) for class AB amplifiers is similar to the class B configuration and is given by the following equation : Where V AC represents the AC fluctuation of the output signal.
When to use negative feedback in class AB amplifiers?
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.