Digital Design problems
- 1. What would be the output voltage of a 7814 voltage regulator?
Options- A. ?14 V dc
- B. +14 V dc
- C. ?8 V dc
- D. +8 V dc Discuss
Correct Answer: +14 V dc
- 2. An optocoupler is an integrated circuit with an LED and a zener diode encased in the same package.
Options- A. True
- B. False Discuss
Correct Answer: False
- 3. Setup time specifies:
Options- A. the minimum time the control levels need to be maintained on the inputs prior to the triggering edge of the clock in order to be reliably clocked into the flip-flop
- B. the maximum time interval required for the control levels to remain on the inputs before the triggered edge of the clock in order for the data to be reliably clocked out of the flip-flop
- C. how long the operator has to get the flip-flop running before the maximum power level is exceeded
- D. how long it takes the output to change states after the clock has transitioned Discuss
Correct Answer: the minimum time the control levels need to be maintained on the inputs prior to the triggering edge of the clock in order to be reliably clocked into the flip-flop
- 4. Can the automatic RC circuit be used to set a flip-flop rather than reset the flip-flop?
Options- A. yes
- B. no Discuss
Correct Answer: yes
- 5. How much setup time (ts) is required for the 74LS76?
Options- A. 5 ns
- B. 10 ns
- C. 20 ns
- D. 40 ns Discuss
Correct Answer: 20 ns
- 6. A 0.01-µF capacitor is recommended by TTL manufacturers for ________ the power supply.
Options- A. decoupling
- B. filtering
- C. rectifying
- D. grounding Discuss
Correct Answer: decoupling
- 7. Why would a delay gate be needed for a digital circuit?
Options- A. A delay gate is never needed.
- B. to provide for setup times
- C. to provide for hold times
- D. to provide for setup times and hold times Discuss
Correct Answer: to provide for setup times and hold times
- 8. Why is the Schmitt trigger needed in the 60-Hz TTL-level clock pulse generator?
Options- A. to provide a triangle wave
- B. to provide a sine wave
- C. to provide a rounded pulse waveform
- D. to provide a sharp pulse waveform Discuss
Correct Answer: to provide a sharp pulse waveform
- 9. Look up the propagation delay from the clock to the output for the 7476. Are the HIGH-to-LOW and LOW-to-HIGH propagation delays the same?
Options- A. yes
- B. no, tPLH = 25 ns, tPHL = 40 ns
- C. no, tPLH = 40 ns, tPHL = 25 ns
- D. no, tPHL = 25 ns, tPLH = 40 ns Discuss
Correct Answer: no, tPLH = 25 ns, tPHL = 40 ns
- 10. In the automatic reset circuit for a flip-flop, how long does it take the capacitor to completely charge?
Options- A. 1 time constant (RC)
- B. 2 time constants (RC)
- C. 5 time constants (RC)
- D. 10 time constants (RC) Discuss
Correct Answer: 5 time constants (RC)
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