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Electronics and Communication Engineering - Digital Electronics

Exercise : Digital Electronics - Section 1
21.
An AND gate has two inputs A and B and one inhibit input 3, Output is 1 if
A = 1, B = 1, S = 1
A = 1, B = 1, S = 0
A = 1, B = 0, S = 1
A = 1, B = 0, S = 0
Answer: Option
Explanation:

All AND inputs must be 1 and inhibit 0 for output to be 1.

22.
The greatest negative number which can be stored is 8 bit computer using 2's complement arithmetic is
- 256
- 128
- 255
- 127
Answer: Option
Explanation:

The largest negative number is 1000 0000 = -128.

23.
A JK flip flop has tpd= 12 ns. The largest modulus of a ripple counter using these flip flops and operating at 10 MHz is
16
64
128
256
Answer: Option
Explanation:

Number of flip-flops = = 8.333 say 8

Modulus = 28 = 256.

24.
The basic storage element in a digital system is
flip flop
counter
multiplexer
encoder
Answer: Option
Explanation:

Storing can be done only in memory and flip-flop is a memory element.

25.
In a ripple counter,
whenever a flip flop sets to 1, the next higher FF toggles
whenever a flip flop sets to 0, the next higher FF remains unchanged
whenever a flip flop sets to 1, the next higher FF faces race condition
whenever a flip flop sets to 0, the next higher FF faces race condition
Answer: Option
Explanation:

In a ripple counter the effect ripples through the counter.

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