Class A power amplifier

OBJECTIVE : To determine efficiency of class A power amplifier.

APPARATUS REQUIRED: TINA PRO SOFTWARE

PC

CIRCUIT DIAGRAM:

THEORY:

The function of power amplifier is to raise the power level of input signal. Class A power amplifier is one in which the output current flows during the entire cycle of input signal. Thus the operating point is selected in such a way that the transistor operates only over the linear region of its load line. So this amplifier can amplify input signal of small amplitude. As the transistor operates over the linear portion of load line the output wave form is exactly similar to the input wave form. Hence this amplifier is used where freedom from distortion is the prime aim.

PROCEDURE:

1. Select different components and place them in the grid.
2. Apply the input ac signal voltage of 60mV (p-p) and simulate the circuit.
3. Observe the output wave form on CRO and measure the output voltage V₀.
4. Now connect the ammeter at collector terminal of transistor.
5. Disconnect the ac signal from input and measure the collector current Ic in ammeter.
6. Calculate the efficiency by using practical calculations compare it with theoretically calculated efficiency.

OBSERVATION :

THEORETICAL CALCULATIONS :

Practical Calculations :

OBSERVATIONS:

WAVEFORM:

INPUT WAVEFORM:

OUTPUT WAVEFORM:

RESULT: The efficiency of class A Power amplifier is verified.

LEARNING OUTCOMES:

Students are able to Design and analyze class A power amplifier.

VIVA QUESTIONS:

1. Define class A power amplifier?
2. Give the reason why class A power amplifier is called as directly coupled power amplifier?
3. What is the efficiency of class A power amplifier?
4. In a power transistor, when the maximum power dissipation takes place?
5. List out the different types of distortions?
6. Define Harmonic distortion?
7. What are Class B, Class C and Class AB amplifiers and which type is used for what application?