2.

Refer to Fig. 5.7.1: If the amplifier is delivering 5W_RMS of audio power to the loudspeaker, what will be the approximate RMS voltage across the transformer primary?

3.

What is the main factor governing the maximum power rating (P_TOT) of a transistor?

4.

For the class B power amplifier circuit in Fig. 5.7.2, which of the output waveforms a b c d shows the correct output signal?

• a)
• b)
• c)
• d)

• a) Class A
• b) Class AB
• c) Class B
• d) Class D

• a) Class A.
• b) Class AB.
• c) Class B.
• d) Class C.

• a) To protect the base emitter junctions of Tr2 and Tr3 from reverse polarity.
• b) To prevent the wrong half cycles of the signal appearing at Tr2 and Tr3 bases.
• c) To provide temperature stabilisation for Tr2 and Tr3 bias.
• d) To eliminate crossover distortion.

• a) AC negative feedback.
• b) Bootstrap capacitor.
• c) Bass Boost.
• d) Mid point decoupling.

• a) A comparator.
• b) A low pass filter.
• c) A pulse width demodulator.
• d) A MOSFET power switch.

• a) PWM produces many even harmonics.
• b) PWM reduces the efficiency of the amplifier.
• c) PWM is more likely to produce RF interference.
• d) PWM output stages require excessively large heat sinks.

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