Transistor audio power amplifier

         

Class-A single ended power amplifier diagram with derivation 

Class-AB power amplifier diagram

Class-c power amplifier diagram

Class-B power amplifier diagram

Class-A power amplifier Diagram

Transistor audio power amplifier

-: TOPICS:- 1. Difference between voltage and power amplifier. 2. Collector efficiency 3. Distortion 4. Power dissipation capability 5. Types of power amplifier  *Class-A power amplifier *Class-B power amplifier *Class-C power amplifier *Class-AB power amplifier 6.Class-A single ended power amplifier

 

*Difference B/W voltage and power amplifier

Voltage amplifier	Power amplifier
1. The main purpose of voltage amplifier to raise voltage level to week signal.	1. The main purpose of power amplifier to raise the power level of the signal.
2. The charactertics of voltage and current are liner during the operation transistor distortion in output will be minimum.	2. The charactertics of voltage and current are non-linear reason of character distortion will be present.
3. Size of the transistor is small.	3. Size of the power amplifier is large.
4. In case of voltage amplifier main parameter under consideration is gain.	4. In p.a main parameter under consideration is collector efficiency.
5. In this rc-coupling is widely used	5. In this transformer coupling is widely used.

 

*Important term in power amplifier.

*Collector Efficiency:- The ratio of the output power to dc input power or zero signal power of a power amplifier is known as collector efficiency. A power amplifier convert D.C to A.C power which is varies according to the input signal.

*Distortion:- The change of output wave form the input waveform of an amplifier is known as distortion. When the output wave shape is note exact replica of the input wave shape, the amplifier is said to have introduction some distortion.

*Power dissipation capability:- The ability of a power transistor to dissipation heat developed in it during operation is known as power dissipation capability.

A power transistor is used in a power amplifier caries large current during operation. These current heats up the collector junction.

 *Types of power amplifier or classification of power amplifier:-

1. Class-A power amplifier

2. Class-B power amplifier

3. Class-C power amplifier

4. Class-AB power amplifier

 

*1.Class-A power amplifier:- The power amplifier in which the operating point is so adjusted that the collector current flows during whole cycle of the input signal are known as class-A power amplifier.

In class-A power amplifier the Q point is set to in the middle of load line. So that the transistor is operate in active region though out full a.c cycle that is the collector current flows for entire AC signal.

*2.Class-B power amplifier:- The power amplifier in which the operating point is so adjusted that the collector current flows only during the positive half cycle of the input signal are known as class-B power amplifier.

The efficiency of class-B power amplifier is 50%.

*3.Class-C power amplifier:- The power amplifier in which collector current flows for less than half cycle of the input signal are known as class-c power amplifier.

The efficiency of Class-C power amplifier is 75%.

*Class-AB power amplifier:- The power amplifier in which the operating point is so adjusted that the collector current flows for more than half cycle but less than full cycle of the input signal are known as Class-AB power amplifier.

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