225. Optocouplers combine
A. Buck regulator
B. Boost regulator
C. Buck-boost regulator
D. Cuk regulator

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226. Which of the following statements are correct? 1. BJTs have positive temperature coefficient 2. Diodes are connected in series to increase the capability 3. The input power factor of controllers, which varies with delay angle, is generally poor, especially at the low output range of these statements
A. 1 and 2 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2 and 3

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227. Inverter gain is given by the ratio
A.dc output voltage ac input voltage
B.ac output voltage ac input voltage
C.dc output voltage dc input voltage
D.ac output voltage dc input voltage

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228. In resonant pulse inverters
A. dc output voltage variation is wide
B. the frequency is low
C. the output voltage is never sinusoidal
D. dc saturation of transformer core is minimised

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229. The efficiency of a expected in the range
A. 50 to 55 percent
B. 65 to 72 percent
C. 82 to 87 percent
D. 92 to 999 percent

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230. Which of the following regulator provides output voltage polarity reversal without a transformer?
A. Buck regulator
B. Boost regulator
C. Buck-boost regulator
D. Cuk regulator

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231. A power MOSFET is a
A. current controlled device
B. voltage controlled device
C. both current and voltage device
D. none of the above

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