Electronics and Communication Engineering - Digital Electronics

6. 

A 4 : 1 multiplexer requires __________ data select line.

A. 1
B. 2
C. 3
D. 4

Answer: Option B

Explanation:

22 = 4. Hence 2 select lines.


7. 

The number of unused states in a 4 bit Johnson counter is

A. 2
B. 4
C. 8
D. 12

Answer: Option C

Explanation:

Total state = 2n = 24 = 16

Used state = 2n = 2 x 4 = 8

Unused state = 16 - 8 = 8.


8. 

It is desired to display the digit 7 using a seven segment display. The LEDs to be turned on are

A. a, b, c
B. b, c, d
C. c, d, e
D. a, b, d

Answer: Option A

Explanation:


9. 

For a MOD-12 counter, the FF has a tpd = 60 ns The NAND gate has a tpd of 25 n sec. The clock frequency is

A. 3.774 MHz
B. > 3.774 MHz
C. < 3.774 MHz
D. 4.167 MHz

Answer: Option A

Explanation:

For a proper working, the clock period should be equal to or greater than

tpd = Mod 12 - 4FFs = 4 x 60 = 240 nsec.

Total tpd = 240 + 25 = 265 nsec.

= fc and fc = 3.774 MHz.


10. 

1001012 is equal to decimal number

A. 47
B. 37
C. 21
D. 17

Answer: Option B

Explanation:

32 + 4 + 1 = 37 in decimal.