t Name: | Alfredo C. Del Junco | Date: | 01/31/2014 |

ET 1410 Exam 2

1. In a zero-level detector, the output changes state when the input __________.

a. is positive

b. is negative

c. crosses zero d. has a zero rate of change

2. The zero-level detector is one application of a_________.

a. comparator

b. differentiator

c. summing amplifier

d. diode

3. Noise on the input of a comparator can cause the output to_________.

a. hang up in one state

b. go to zero

c. change back and forth erratically between two states

d. produce the amplified noise signal

4. The effects of noise in a comparator circuit can be reduced by_________.

a. using negative feedback

b. using positive feedback

c. using hysteresis

d. answers (b) and (c)

5. A comparator with hysteresis_________.

a. has one trigger point

b. has two trigger points

c. has a variable trigger point

d. is like a magnetic circuit

6. A window comparator detects when_________.

a. the input is between two specified limits

b. the input is not changing

c. the input is changing too fast

d. the amount of light exceeds a certain value

7. If the voltage gain for each input of a summing amplifier with a 4.7 kΩ feedback resistor is unity, the input resistors must have a value of_________.

a. 4.7 kΩ

b. 4.7 kΩ divided by the number of inputs

c. 4.7 kΩ times the number of inputs

d. Unity gain cannot be achieved unless the feedback resistor becomes zero.

8. An averaging amplifier has five inputs. The ratio Rf /Rin must be_________.

a. 5

b. 0.2

c. 1

d. 2

9. In a scaling adder, the input resistors are_________.

a. all the same value

b. all of different values

c. each proportional to the weight of its inputs

d. related by a factor of two

10. In an integrator, the feedback element is a_________.

a. resistor

b. capacitor

c. zener diode

d. voltage divider

11. For a step input, the output of an integrator is a_________.

a. pulse

b. triangular waveform

c. spike

d. ramp

12. In a differentiator, the feedback element is a_________.

a. resistor

b. capacitor

c. zener diode

d. voltage divider

13. The output of a differentiator is proportional to_________.

a. the RC time constant

b. the rate at which the input is changing

c. the amplitude of the input

d. answers (a) and (b)

14. The term pole in filter terminology refers to_________.

a. a high-gain op-amp

b. one complete active filter

c. a single RC network

d. the feedback circuit

15. A single resistor and a single capacitor can be connected to form a filter with a roll-off rate of_________. a. -20 dB/decade

b. -40 dB/decade

c. -6 dB/octave

d. answers (a) and (c)

16. A band-pass response has_________.

a. two critical frequencies

b. one critical frequency

c. a quality factor of larger than 10

d. a center frequency lower than the critical frequencies

17. The lowest frequency passed by a low-pass filter is_________.

a. 1 Hz

b. 0 Hz

c. 10 Hz

d. dependent on the critical frequency

18. The Q of a band-pass filter depends on_________.

a. the critical frequencies

b. only the bandwidth

c. the center frequency and the bandwidth

d. only the center frequency

19. The damping factor of an active filter determines_________.

a. the voltage gain

b. the critical frequency

c. the response characteristic

d. the roll-off rate

20. The damping factor of a filter is set by_________.

a. the negative feedback circuit

b. the positive feedback circuit

c. the frequency-selective circuit

d. the gain of the op-amp

21. If the value of R1 in Figure 1(below) is less than specified, the output voltage will_________.

a. increase

b. decrease

c. not change

d. change polarity

+3 V
+1.8 V
Vout
+3 V
+1.8 V
Vout

Figure 1

22. In reference to Figure 2 (next page), if C is open, the rate of change of the output voltage in response to the step input will_________.

a. become the slew rate

b. decrease

c. not change

d. increase and reverse polarity

Figure 2

23. In reference to Figure 2 (above), if C is open the maximum voltage at the output will_________.

a. be maximum positive output voltage

b. remain at current level

c. be maximum negative output voltage

d. become zero

24. In reference to Figure 3 (next page), if the value of R is larger than specified, the output voltage in response to the periodic triangular input waveform will_________.

a. increase proportional to R

b. decrease proportional to R

c. not change

d. become unspecified

25. In reference to Figure 3 (below), if the value of R doubles, the period of the output will _________.

a. be 2 times the period of the input

b. be half the period of the input

c. not change

d. lock in at maximum positive output voltage

Figure 3