# MCQs on Digital Electronics

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01․ Combinations that are not listed for the input variables are
Overflow
Carry
Borrow
Don't Care

Don't Cares are the combination of inputs for those the value output does not matter or changes.

02․ What is the minimum number of 2 input NAND gates used to perform the function of 2 input OR gate
1
2
3
4

Three number of 2 input Nand gate is required to perform the function of 2 input OR gate by the help of De morgan's law.

03․ Which circuit is used in between two systems having two different codes
Sequential
Combinational
Both A and B
Conversion

Both the sequential circuit and combinational circuit are not used for two different codes. If we need to convert one code to another, we need conversion technique. So, we need a converter.

2 inputs, 2 outputs
3 inputs, 2 outputs
2 inputs, 1 output
3 inputs, 1 output

A full adder has three inputs as augend bit, addend bit and carry input. It has two output as a sum and a carry output.

1 input and 1 output
2 inputs and 2 output
1 input and 2 outputs
2 inputs and 1 outputs

A half adder has two input has augend bit and addend bit. It has two output has as one sum and a carry.

06․ The switch which clears a flip-flop is know as
Reset
Clear
Both A and B
None

Reset or Clear is the signal which makes the state of the flip-flop cleared. for both input Q = 0, Q' = 1 the flip-flop is cleared.

07․ Master-slave flip flop consists of ________ flip-flop(s).
1
2
3
4

Master-slave flip flop consists of two flip-flops. One flip-flop serve as MASTER and the other as SLAVE.

08․ The momentary change in the output/state of the flip-flops is known as
tri-state
unstable state
inverter
trigger

Output of the flip flop can be changed by changing small amount of input signal. The small change is done by applying a trigger pulse.

09․ The state of a flip-flop can be switched by changing its ________ signals.
input
output
triggering
clearing

Input signals can change the output only in the case when the Clock signal is enabled.

10․ X' AND X' will result
1
0
X
X power 2

In digital system AND function with itself will result always result the same value. Check it by putting 1 and 0 as well.

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