Question
In Figure E7-1, what is the purpose of R3?
Answer Options
- A) Fixed bias
- B) Emitter bypass
- C) Output load resistor
- D) Self bias
Correct Answer: D
Explanation
Figure E7-1 shows a common emitter amplifier. R3 is the resistor placed between the emitter terminal and ground. Its primary function is to provide stabilization against temperature changes, which can drastically alter the transistor’s operating point.
The purpose of R3 is to provide Self bias (also called emitter stabilization). As the transistor heats up, its collector current tends to increase. This increased current flows through R3}, increasing the voltage drop across it. This increased emitter voltage reduces the forward-bias on the base-emitter junction, forcing the collector current back down, thereby stabilizing the operating point against thermal drift.
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