# Combinational Circuits MCQ’s

This set of Digital Circuits Multiple Choice Questions & Answers (MCQs) focuses on “Combinational Circuits”.

1. For a two-input XNOR gate, with the input waveforms as shown below, which output waveform is correct?

a) d
b) a
c) c
d) b

2. The device shown here is most likely a ________

a) Comparator
b) Multiplexer
c) Inverter
d) Demultiplexer

3. Which of the circuits in figure (a to d) is the sum-of-products implementation of figure (e)?

a) a
b) b
c) c
d) d

4. 3 bits full adder contains ________
a) 3 combinational inputs
b) 4 combinational inputs
c) 6 combinational inputs
d) 8 combinational inputs

5. What is the indication of a short to ground in the output of a driving gate?
a) Only the output of the defective gate is affected
b) There is a signal loss to all load gates
c) The node may be stuck in either the HIGH or the LOW state
d) The affected node will be stuck in the HIGH state

6. The carry propagation can be expressed as ________
a) Cp = AB
b) Cp = A + B
c) All but Y0 are LOW
d) All but Y0 are HIGH

7. What type of logic circuit is represented by the figure shown below?

a) XOR
b) XNOR
c) AND
d) XAND

8. For the device shown here, assume the D input is LOW, both S inputs are LOW and the input is LOW. What is the status of the Y’ outputs?

a) All are HIGH
b) All are LOW
c) All but Y0 are LOW
d) All but Y0 are HIGH

9. Which of the following logic expressions represents the logic diagram shown?

a) X=AB’+A’B
b) X=(AB)’+AB
c) X=(AB)’+A’B’
d) X=A’B’+AB

10. Which of the following combinations of logic gates can decode binary 1101?
a) One 4-input AND gate
b) One 4-input AND gate, one inverter
c) One 4-input AND gate, one OR gate
d) One 4-input NAND gate, one inverter