Electronics and Communication Engineering - Digital Electronics

41. 

TTL is used in electronic calculators.

A. True
B. False

Answer: Option B

Explanation:

Calculators use CMOS.


42. 

Inverter 74 LS04 has following specifications I0H max = - 0.4 mA, I0L max = 8 mA, IIH max = 20 μA, IIL max = 0.1 mA
The fan out of this inverter is

A. 10
B. 20
C. 60
D. 100

Answer: Option B

Explanation:

Fan out in low state = = 80 Fan out in high state = Hence fan out is smaller of two values ie., 20.


43. 

A 4 bit ripple counter starts in 0000 state. When the counter reads 0010 the number of clock pulses which have occurred is

A. 2
B. 18
C. 2 or 18
D. 2 or 18 or 34

Answer: Option D

Explanation:

At pulse 1 the state changes to 0001 and at pulse 2 it changes to 0010 Since it has a total of 16 states, the counter returns to 0000 after 16 and 32 pulses.


44. 

The number FF in hexadecimal system is equivalent to number __________ in decimal system.

A. 256
B. 255
C. 240
D. 239

Answer: Option B

Explanation:

FF = 15 x 16 + 15 = 255.


45. 

The inputs A, B, C of the given figure are applied to a 3 input NOR gate. The output is

A. HIGH from 4 to 0
B. LOW from 0 to 4
C. HIGH from 0 to 1 and LOW from 1 to 4
D. LOW from 0 to 2 and HIGH from 2 to 4

Answer: Option C

Explanation:

NOR gate gives high output if all inputs are Low. For all other combinations of inputs, output is Low.