Teach Yourself Electricity and Electronics, 5th edition

Stan Gibilisco

Explanations for Quiz Answers in Chapter 28

1. We can control the gain of an op amp by using negative feedback, usually by placing a resistor or potentiometer between the output and the inverting input. Reducing the gain in this way can keep the op amp from oscillating. The correct choice is (b).

2. We find both N-channel and P-channel MOSFETs in a CMOS (complementary-metal-oxide-semiconductor) logic chip. The correct answer is (c).

3. If we intend to use an IC to construct an analog circuit of any kind, we should choose a linear IC. The correct answer is (b). All of the other choices indicate digital ICs.

4. Resistors, capacitors, and transistors can all be fabricated onto semiconductor ICs without difficulty, but inductors pose a problem (except for extremely small values). The correct choice is (c).

5. An integrator circuit will shift the phase of a pure sine-wave input signal so that the output lags the input by 90º. We can use an op amp to build an integrator. The correct choice is (a). All of the other choices indicate digital ICs that would not work in this analog application.

6. In a DRAM (dynamic random-access memory) chip, the data is stored in the form of electrical charges on capacitors etched onto the semiconductor material. The correct choice is (d).

7. A discrete-component circuit or device can generally handle more power than an IC that performs the same function. However, the IC will usually allow easier maintenance and also will enhance the reliability. The only answer that works here is (a).

8. We can never overwrite the data in a plain ROM (read-only memory) chip, so (a) is wrong. We can overwrite data in an EPROM (erasable programmable read-only memory) chip or an EEPROM (electrically erasable programmable read-only memory) chip, so (b) and (c) might work. However, we can quickly and easily overwrite the data in a RAM (random-access memory) chip; we need do nothing more than input the new data. The best choice is (d).

9. When we work with MOS (metal-oxide-semiconductors) devices of any kind, we must exercise caution to avoid destroying the component by subjecting it to an electrostatic buildup. Even a small discharge can ruin a MOS, NMOS, PMOS, or CMOS chip. The correct choice is (a).

10. If we apply a pure AC sine-wave signal to an integrator IC, we get another sine wave at the output, but the phase is shifted 90º to the right (1/4 cycle later in time). The correct choice is (b).

11. If we can remove external power from a memory IC and have the data remain intact nevertheless, we have nonvolatile memory. The correct choice is (d).

12. A chip in LSI (large-scale integration) chip can have up to 1000 transistors, while a chip in VLSI (very-large-scale integration) can have up to 10,000 transistors. The premise of the question is wrong. The correct choice is (d).

13. You would not expect to see an IC as the main component of a power-supply filter (they comprise discrete capacitors and sometimes also inductors), so (a) won't work. The final amplifier in a TV broadcast transmitter requires far too much power for any IC to handle, so (b) is wrong. You would see an IC as the main component in an electronic calculator, however, so choice (c) is correct.

14. A comparator IC can trigger external devices or systems such as alarms, lights, or sirens, so choice (a) looks good. An EPROM chip can't do that all by itself, so (b) is wrong. A notch filter or a multiplexer has nothing to do with triggering external components, so (c) and (d) are both wrong. The right answer is (a).

15. When we talk about the component density in an IC, we usually refer to the overall number of individual components (such as transistors) on the chip. The correct answer is (d).

16. If we provide a differentiator circuit with a constant DC input voltage of any reasonable positive or negative value, we get a zero-voltage, constant output -- no signal whatsoever. Remember, the derivative of a function is another function that expresses the slope of the first function, point-by-point. A constant DC voltage is represented as a constant function, which graphs as a straight, horizontal line. The slope of such a line, and therefore the derivative of the constant function, equals zero at every point. The correct choice is (b).

17. In order to reprogram a typical EPROM (erasable programmable read-only memory) chip, we must expose it to UV (ultraviolet) rays. The correct choice is (b).

18. When we use ECL (emitter-coupled logic), we obtain high speed, and the device doesn't require much current. The working life of ECL is comparable with that of TTL (transistor-transistor logic). However, because TTL always operates either in cutoff or saturation while ECL "hovers" in a state where analog gain is possible, ECL exhibits more sensitivity to noise than TTL does. The correct choice is (c).

19. We can overwrite data in a RAM chip with ease. We can overwrite the data in an EPROM or EEPROM chip if we're willing to go to a little trouble. However, we can't overwrite data in a ROM chip. The correct answer is (a).

20. If we apply a pure AC sine-wave signal to a differentiator IC, we get another sine wave at the output, but the phase is shifted 90º to the left (1/4 cycle earlier in time). The correct choice is (b).