Electrical Engineering Objective Questions { Material And Components }

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274. The collector capacitance reduces the voltage amplification of a common-base amplifier at high frequencies bacause

A. Alpha is reduced

B. Beta is reduced

C. the effective output resistance is decreased

D. the effective output resistance is increased

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275. The breakdown voltage of the emitter junction is usually

A. much smaller than the collector junction breakdown voltage much larger than the collector-junction breakdown voltage

C. (f) due punch-through

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276. If a transistor is operated at a frequency above the alpha cutoff frequency

A. the transistor will burn out

B. there will be no output power

C. the emitter junction must be forward-biased

D. the output current will be reduced

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277. Alpha cutoff frequency is the frequency, where

A. Alpha becomes zero

B. output power is reduced to one-tenth its original value

C. Alpha becomes 0.7 times its original value

D. Punch-through occurs

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278. When determining the common-emitter current gain by making small changes in direct currents, the collector voltage is held constant so that

A. the transistor will not be burned out

B. the change in emitter current will be due to a change in collector current

C. the output resistance will be high

D. the change in collector current will be due only to a change in base current

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279. The high resistance of the reversebiased collector junction is due to the fact that

A. a small change in emitter current causes an almost equal change in collector current

B. a small change in emitter bias voltage causesa large change in collector current

C. a large change in collector bias voltage causes very little change in collector current

D. a small change in collector bias voltage causes a large change in collector current

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280. A heat sink is used to

A. heat the transistor to its maximum operating temperature

B. keep transistors warm when not in use

C. receive heat from the transistor and dissipate it to the surrounding air (d) receive heat from the surrounding air and deliver it to the transistor

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