A class A power amplifier delivers a maximum AC output of 10 W. What is the minimum power rating required for the transistor used?
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Answer: D. 20 W
Explanation
A class A power amplifier requires a transistor power rating of at least twice the maximum AC output power to safely dissipate idle heat. Class A amplifiers conduct continuous collector current even with zero input signal, resulting in maximum power dissipation at rest. Selecting a transistor with double the maximum output power rating prevents thermal overload and premature semiconductor junction destruction. Class A power amplifiers bias their active transistors to conduct across the entire three hundred sixty degree input signal cycle. Maximum theoretical efficiency for a resistively loaded class A amplifier is twenty-five percent, meaning most DC input power becomes heat. Transistor maximum power dissipation specifications dictate safe operating temperature thresholds required for reliable continuous amplification.
A 10 W rating matches the AC output power exactly, which would cause the transistor to burn out instantly from excessive idle heat. A 15 W rating is insufficient because class A amplifiers must dissipate idle power equal to double their maximum AC output capability. A 20 W rating correctly doubles the 10 W AC output, ensuring the transistor handles maximum continuous thermal dissipation safely.
- Subject
- Engineering
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- Electrical Engineering
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- Difficulty
- medium
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