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Electronics and Communication Engineering - Digital Electronics

Exercise : Digital Electronics - Section 4
41.
TTL is used in electronic calculators.
True
False
Answer: Option
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
10
20
60
100
Answer: Option
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
2
18
2 or 18
2 or 18 or 34
Answer: Option
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.
256
255
240
239
Answer: Option
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
HIGH from 4 to 0
LOW from 0 to 4
HIGH from 0 to 1 and LOW from 1 to 4
LOW from 0 to 2 and HIGH from 2 to 4
Answer: Option
Explanation:

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

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