GATE EE
Digital Electronics
Combinational Circuits
Previous Years Questions

Marks 1

Consider the following circuit which uses a $$2$$-to-$$1$$ multiplexer as shown in the figure below. The Boolean expression for output $$F$$ in terms ...
In the $$4 \times 1$$ multiplexer, the output $$F$$ is given by $$F = A \oplus B.$$ Find the required input $${{\rm I}_3}{{\rm I}_2}{{\rm I}_1}{{\rm I...
The output $$Y$$ of a $$2$$ $$-$$ bit comparator is logic $$1$$ whenever the $$2$$-bit input $$A$$ is greater than the $$2$$-bit input $$B.$$ The numb...
The output $$Y$$ of the logic circuit given below is ...
Figure shows a $$4$$ to $$1$$ $$MUX$$ to be used to implement the sum $$S$$ of a $$1$$-bit full adder with input bits $$P$$ and $$Q$$ and the carry in...
The output $$f$$ of the $$4$$- to- $$1$$ $$MUX$$ shown in fig. is ...

Marks 2

A Boolean function $$f\left( {A,B,C,D} \right) = \Pi \left( {1,5,12,15} \right)$$ is to be implemented using an $$8 \times 1$$ multiplexer ($$A$$ is $...
Two monoshot multivibrators, one positive edge triggered $$\left( {{M_1}} \right)$$ and another negative edge triggered $$\left( {{M_2}} \right)$$ are...
A $$3$$-bit gray counter is used to control the output of the multiplexer as shown in the figure. The initial state of the counter is $${000_2}.$$ The...
A $$3$$ line to $$8$$ line decoder, with active low outputs, is used to implement a $$3$$- variable Boolean function as shown in the figure: The simpl...
A $$4 \times 1\,\,MUX$$ is used to implement a $$3$$- input Boolean function as shown in figure. The Boolean function $$F\left( {A,\,\,B,\,\,C} \right...
The minimal product-of-sums function described by the $$K$$-map given in Fig. ...
The logic function $$F = AC + ABD + ACD$$ is to be realized using an $$8$$ to $$1$$ multiplexer shown in figure, using $$A, C$$ and $$D$$ as control i...
Match the following ...

Marks 5

In a digital combinational circuit with $$4$$ inputs $$(A, B, C, D),$$ it is required to obtain an output of logical $$1$$ only for the input combinat...
A $$3$$-input $$2$$-output priority encoder has the following truth table where $$'X'$$ indicate don't care conditions. Realize the logic using $$NAND...
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