1. A silicon power transistor is operated with a heat sink ( SA = 1.5ºC/W). The transistor, rated at 150 W (25ºC), has JC = 0.5º C/W, and the mounting insulation has CS = 0.6 ºC/W. What is the maximum power that can be dissipated if the ambient temperature is 50ºC and TJmax = 200 ºC?
2. Refer to this figure. The dc voltage on the collector, VC, is
3. What is the ratio of the secondary voltage to the primary voltage with the turn ratio in the windings?
4. Class ________ amplifiers are normally operated in a push-pull configuration in order to produce an output that is a replica of the input.
5. You find that there is an input signal on the base of Q1 and Q2. However, there is no output signal. You then measure the dc voltages on Q2 and find them to be all 0 V. The possible trouble might be
6. Which type of power amplifier is biased for operation at less than 180º of the cycle?
7. Class AB operation is ________ operation.
8. The principal advantage(s) of MOSFETs over BJTs is (are)
9. Which of the following instruments allows more precise measurement of the harmonic components of a distorted signal?
10. In class B operation, at what fraction of VCC should the level of VL(p) be to achieve the maximum power dissipated by the output transistor?
11. What is the maximum temperature rating for silicon power transistors?
12. What is the maximum efficiency of a class A circuit with a direct or series-fed load connection?
13. You have an oscilloscope across RL and it shows a zero signal voltage. The problem might be that
14. Which class of amplifier operates in the linear region for only a small part of the input cycle?
15. The Q-point is at cutoff for class ________ operation.
16. Determine what maximum dissipation will be allowed for a 70-W silicon transistor (rated at 25ºC) if derating is required above 25ºC by a derating factor of 0.6 W/ºC at a case temperature of 100º.
17. How many transistors must be used in a class B power amplifier to obtain the output for the full cycle of the signal?
18. What transformer turns ratio is required to match an 8- speaker load so that the effective load resistance seen at the primary is 12.8 k?
19. Which of the following is (are) power amplifiers?
20. Refer to the figure. The maximum efficiency of this amplifier is
21. Quiescent power is the power dissipation of a transistor
22. Which of the power amplifiers is not intended primarily for large-signal or power amplification?
23. Refer to this figure. This amplifier is operating as a ________ amplifier.
24. By how much does the output signal vary for a class AB power amplifier?
25. Which type of amplifier uses pulse (digital) signals in its operation?