Q-Which gates in Digital Circuits are required to convert a NOR-based SR latch to an SR flip-flop?
a) Two 2 input AND gates
b) Two 3 input AND gates
c) Two 2 input OR gates
d) Two 3 input OR gates
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Answer: a
Explanation: Two 2 input AND gates are placed with a NOR – based S – R latch to convert it to an S – R flip – flop. One AND gate is given R in one input and clock in the other. Similarly the second AND gate is given S in one input and clock in the other.
Q-Which of the following majorly determines the number of emitters in a TTL digital circuit?
a) Fan – in
b) Fan – out
c) Propagation delay
d) Noise immunity
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Answer: a
Explanation: The TTL circuit uses multi – emitter transistors with many emitters in the input. Thus, the number of emitters is determined by the fan – in. Fan – in determines the number of inputs the particular gate can handle.
Q-Which of these flip – flops cannot be used to construct a serial shift register?
a) D – flip flop
b) SR flip – flop
c) T flip – flop
d) JK flip – flop
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Answer: c
Explanation: SR, D, and JK flip flops can be used to construct a serial shift register. A T flip – flop gives the output 0 when input 1 is given and gives output 1 when input 0 is given. Thus, it cannot be used as a serial shift register.
Q-Which of the following options correctly represent the characteristic of Excess – 3 code?
a) It is a reflexive as well as a sequential code
b) It is a reflexive code but not a sequential code
c) It is a sequential code but not a reflexive code
d) It is neither a reflexive code nor a sequential code
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Answer: a
Explanation: A reflexive code is a code where the code for 9 is the complement of code for 0 and so on. A sequential code is a code where each succeeding code is one binary number more than the preceding code. Excess – 3 code satisfies both these properties.
Q-Which of the following points is not correct regarding an Ex – NOR gate in Digital Electronics?
a) It is a one – bit comparator
b) It is a buffer
c) It is a one – bit inverter
d) It is a universal gate
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Answer: a
Explanation: Ex – NOR gate is a one – bit comparator as the output for the gate is 1 if similar inputs are given to the gate and output is 0 if different inputs are given to the gate
Q-Which of these pins will allow to activate and deactivate a multiplexer?
a) Enable pin
b) Selection pin
c) Logic pin
d) Preset pin
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Answer: a
Explanation: An enable pin allows to activate and deactivate the multiplexer. When enable pin is 0, the output is obtained while when enable pin is 0, the multiplexer is disabled.
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