How does a class AB amplifier work?
Class AB amplifiers combine Class A and Class B to achieve an amplifier with more efficiency than Class A but with lower distortion than class B. This is achieved by biasing both transistors so they conduct when the signal is close to zero (the point where class B amplifiers introduce non-linearities).
What is the operating angle of class AB amplifier?
The conduction angle of class AB amplifier is somewhere between 180o to 360o depending upon the operating point selected. This is understood with the help of below figure. The small bias voltage given using diodes D1 and D2, as shown in the above figure, helps the operating point to be above the cutoff point.
When does distortion occur in an AB amplifier?
The transistors do not go into its full off range. This is achieved by implementing two diodes in the circuit. With AB amplifiers, distortion is worst when the signal is at its minimum value. Paradoxically, the distortion is at its lowest when the signal reaches it clipping point.
How to develop an amplifier with low distortion?
In order to develop an amplifier with the low distortion of the Class A configuration along with the high efficiency output of Class B configuration is to build an amplifier circuit which is a combination of the previous two classes resulting in an advanced type of amplifier called Class AB amplifier.
What are the worst bias arrangements for class AB amplifiers?
The worst bias arrangements for Class AB amplifiers with respect to thermal runaway are those that use bias voltages that are relatively fixed over temperature. A resistive voltage divider network provides bias voltages that are relatively fixed with temperature, and this is why they are not widely used as Class AB amplifier bias circuits.
What is the power output of a class AB amplifier?
Class AB Amplifier. We have seen that the power output of an amplifier is the product of the voltage and current, (P = V*I) applied to the load, while the power input is the product of the DC voltage and current taken from the power supply.