Placing a resistor in the emitter leg of a common amplifier helps stabilize the dc operating point against changes in____________?
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Answer: C. Both Temperature & β
Explanation
Adding an unbypassed emitter resistor provides negative feedback that stabilizes the DC operating point. Temperature changes and transistor beta variations shift collector currents if left uncompensated. Emitter resistor feedback counteracts these shifts, stabilizing DC bias against both temperature and beta. Transistor operating points drift when ambient temperatures alter semiconductor junction characteristics. Manufacturing variations cause beta values to differ between identical transistor part numbers. DC biasing stabilization ensures amplifiers do not clip signals due to thermal runaway.
Discrete transistor amplifier design always incorporates emitter resistors for thermal stabilization. Industrial electronics equipment relies on stable DC operating points to function across wide temperatures. Circuit reliability improves significantly when bias stabilization prevents thermal runaway conditions. Option A is wrong because emitter resistors stabilize against transistor beta variations in addition to temperature. Option B is incorrect because emitter resistors also stabilize against temperature induced leakage changes. Option D is incorrect because option C correctly includes both temperature and beta stabilization.
- Subject
- Engineering
- Category
- Electrical Engineering
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- —
- Difficulty
- medium
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