An RC circuit used in a nonretriggerable 74121 one-shot has an REXT of 49 k? and

CuriousTab

CuriousTab

Home Aptitude

Discussion

Home ‣ Digital Electronics ‣ Flip-Flops Comments

Question
An RC circuit used in a nonretriggerable 74121 one-shot has an R_EXTof 49 kΩ and a C_EXT of 0.2 µF. The pulse width (t_W) is approximately ________.
Options
A. 6.9 µs
B. 6.9 ms
C. 69 ms
D. 690 ms

Correct Answer

6.9 ms

Flip-Flops problems

Search Results

2. In VHDL, how is each instance of a component addressed?
Options
A. A name followed by a colon and the name of the library primitive
B. A name followed by a semicolon and the component type
C. A name followed by the library being used
D. A name followed by the component library number

4. The circuit given below fails to function; the inputs are checked with a logic probe and the following indications are obtained: CLK, J1, J2, J3, K1, K2, and K3 are pulsing. Q and are HIGH. and PRE are LOW. What could be causing the problem?
Options
A. There is no problem.
B. The clock should be held HIGH.
C. The PRE is stuck LOW.
D. The CLR is stuck HIGH.

6. In a 555 timer, three 5 kΩ resistors provide a trigger level of ________.
Options
A. 1/4 V_CC and a threshold level 1/2 V_CC
B. 1/3 V_CC and a threshold level 3/4 V_CC
C. 1/3 V_CC and a threshold level 2/3 V_CC
D. 1/4 V_CC and a threshold level 2/3 V_CC

8. On a positive edge-triggered S-R flip-flop, the outputs reflect the input condition when ________.
Options
A. the clock pulse is LOW
B. the clock pulse is HIGH
C. the clock pulse transitions from LOW to HIGH
D. the clock pulse transitions from HIGH to LOW

10. Four J-K flip-flops are cascaded with their J-K inputs tied HIGH. If the input frequency (f_in) to the first flip-flop is 32 kHz, the output frequency (f_out) is ________.
Options
A. 1 kHz
B. 2 kHz
C. 4 kHz
D. 16 kHz

Comments

More in Digital Electronics: