If a diode is connected across resistor RB (positive end up) in the given figure

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Question
If a diode is connected across resistor R_B (positive end up) in the given figure, what is the new duty cycle of the output waveform?
Options
A. 56%
B. 44%
C. 21.6%
D. 17.4%

Correct Answer

21.6%

Multivibrators and 555 Timer problems

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1. In a typical IC monostable multivibrator circuit, at the falling edge of the trigger input, the output switches HIGH for a period of time determined by the ________.
Options
A. value of the RC timing components
B. amplitude of the input trigger
C. frequency of the input trigger
D. magnitude of the dc supply voltage

2. If V_cc of a 555 timer circuit is set to +10 V what is the level of output voltage from the circuit?
Options
A. V_OH = 10 V, V_OL = 0 V
B. V_OH = 10 V, V_OL = 0.1 V
C. V_OH = 8.5 V, V_OL = 0 V
D. V_OH = 8.5 V, V_OL = 0.1 V

3. When the inputs to a flip-flop are changing at the same time that the active trigger edge of the input clock is making its transition, this condition is called:
Options
A. racing
B. toggling
C. slave loading
D. pulse timing

5. The output of a standard TTL NAND gate is used to pull an LED indicator LOW. The LED is in series with a 470-Ω resistor. What is the current in the circuit when the LED is on?
Options
A. 7.02 mA
B. 8.51 mA
C. 10.63 mA
D. 5.32 mA

6. To obtain a 50% duty cycle in an astable 555 timer circuit:
Options
A. t_LO = t_HI
B. R_A = R_B and short R_B with a diode during the capacitor charging cycle
C. capacitor voltage must rise above 1/3 V_CC
D. t_LO = t_HI, R_A = R_B, and short R_B with a diode during the capacitor charging cycle

10. Determine t_HI and t_LO for the circuit given below.
Options
A. t_HI = 7.95 µs, t_LO = 6.24 µs
B. t_HI = 6.24 µs, t_LO = 7.95 µs
C. t_HI = 3.97 µs, t_LO = 3.21 µs
D. t_HI = 3.21 µs, t_LO = 3.97 µs

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