Multivibrators and 555 Timer Questions and Answers
Multivibrators and 555 Timer questions with answers help electronics aspirants strengthen their understanding of pulse generation and timing circuits. The 555 timer IC is widely used in monostable, astable, and bistable multivibrator configurations, making it a frequent topic in exams like DRDO, ISRO, and GATE. Mastering these circuits enhances conceptual clarity in waveform generation, duty cycle control, and timing applications. This section provides well-explained aptitude questions and answers that simulate actual electronics exams, helping students test their theoretical knowledge through practical problem-solving. Whether preparing for technical interviews or competitive electronics tests, this topic gives you an edge through step-by-step solutions and real-world applications of timing circuits.
Multivibrators and 555 Timer
21. A retriggerable one shot has a pulse of 10 ms. 3 ms after being triggered, another trigger pulse is applied. The resulting output pulse will be ________ ms.
- 3
- 7
- 10
- 13
22. What is another name for a bistable multivibrator?
- an on-off switch
- an oscillator
- a flip-flop
24. Which mode of operation is being used when a 555 timer chip has two external resistors and an external capacitor?
- monostable
- pulse stretching
- Schmitt triggering
- astable
25. Which of the following is NOT a characteristic of a retriggerable monostable multivibrator?
- It is a dual multivibrator.
- It has an active-HIGH reset, which terminates all timing functions.
- It has no internal timing resistor.
- none of the above
26. The pulse width out of a one-shot multivibrator increases when the:
- supply voltage increases
- timing resistor decreases
- UTP decreases
- timing capacitance increases
27. If the resistor in the Schmitt trigger astable multivibrator is a variable resistor, what part of the output voltage waveform will change when the resistance is changed?
- the shape of the waveform
- the amplitude of the waveform
- the period of the waveform
- none of the above
28. If Vcc of a 555 timer circuit is set to +10 V what is the level of output voltage from the circuit?
- VOH = 10 V, VOL = 0 V
- VOH = 10 V, VOL = 0.1 V
- VOH = 8.5 V, VOL = 0 V
- VOH = 8.5 V, VOL = 0.1 V
29. When extremely critical timing is required, a quartz crystal can be used.
- TRUE
- FALSE
30. In the 74121, which is nonretriggerable, any triggers that come in before the end of the timing cycle are ignored.
- TRUE
- FALSE