Question

Transistor when used as a power amplifier is generally mounted on a metallic plate so as to
1. improve its frequency response
2. Improve the efficiency
3. dissipate the excessive heat developed during working
4. perform all the above stated functions

Answer 1

Correct Answer - Option 3 : dissipate the excessive heat developed during working

Power Amplifier:

• Power amplifiers deal with high voltage amplification (in Volts range instead of normal mV range). generating a lot of heat.
• Since metals are good thermal conductors, the transistors used in them are mounted on the metallic plate as they help radiate the heat dissipated from transistors.
• Power amplifiers are also having low output impedance to match to the load. 
• The common collector or emitter follower circuit is normally used as the power amplifier because it has a low o/p impedance. 
• Due to the use of heat sinks and large size power transistors, the power amplifiers’ become bulky.
• A transformer may also be used for impedance matching on the o/p side.​