GATE ECE
Digital Circuits
Combinational Circuits
Previous Years Questions

## Marks 1

Consider the 2-bit multiplexer (MUX) shown in the figure. For OUTPUT to be the XOR of C and D, the values for A0, A1, A2 and A3 are ___________. ...
Consider the circuit shown in the figure. The Boolean expression F implemented by the circuit is ...
A 4:1 multiplexer is to be used for generating the output carry of a full adder. A and B are the bits to be added while 𝐶in is the input carry and �...
In a half-subtractor circuit with X and Y as inputs, the Borrow (M) and Difference (N = X - Y) are given by
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 number of combinations for which the ...
The logic function implemented by the circuit below is (ground implies a logic "0" ...
The Boolean function f implemented in the figure using two input multiplexers is ...
With out any additional circuitry, an 8:1 MUX can be used to obtain
A 2-bit binary multiplier can be implemented using
The output of the circuit shown in figure is equal to ...
The logic realized by the circuit shown in figure is ...
The minimum function that can detect a "divisible by 3" 8421 BCD code digit (representation is D8 D4 D2 D1) is given by:...

## Marks 2

A four-variable Boolean function is realized using 4 $$\times$$ 1 multiplexers as shown in the figure. The minimized expression for F(U, V, W, X) i...
A programmable logic array (PLA) is shown in the figure. The Boolean function F implemented is ...
Figure I shows a 4-bits ripple carry adder realized using full adders and Figure II shows the circuit of a full-adder (FA). The propagation delay of...
For the circuit shown in the figure, the delays of NOR gates, multiplexers and inverters are 2 ns, 1.5 ns and 1 ns, respectively. If all the inputs P,...
Identify the circuit below. ...
The functionality implemented by the circuit below is ...
A 1-to-8 demultiplexer with data input D$$_{in}$$ , address inputs S$$_{0}$$, S$$_{1}$$, S$$_{2}$$ (with S$$_{0}$$ as the LSB) and $${\overline Y _0}... A 16-bit ripple carry adder is realized using 16 identical full adders (FA) as shown in the figure. The carry-propagation delay of each FA is 12 ns an... An 8-to-1 multiplexer is used to implement a logical function Y as shown in the figure. The output Y is given by ... In the circuit shown, 𝑊𝑊 and 𝑌𝑌 are MSBs of the control inputs. The output 𝐹𝐹 is given by ... If X and Y are inputs and the Difference (D = X – Y) and the Borrow (B) are the outputs, which one of the following diagrams implements a half-subtra... The Boolean function realized by the logic circuit shown is ... What are the minimum number of 2-to 1 multiplexers required to generate a 2-input AND gate and a 2-input EX-OR gate? For the circuit shown in the following figure$${I_0}$$-$${I_3}$$are inputs to the 4:1 multiplexer R(MSB) and S are control bits. tHE OUTPUT Zcan b... In the following circuit, X is given by ... The minimum number of 2 to 1 multiplexers required to realize a 4 to 1 mutliplexer is The circuit shown in figure converts ... The circuit shown in figure has 4 boxes each described by inputs P, Q, R and outputs Y, Z with Y =$$\,P \oplus \,Q\, \oplus \,R$$z=$$RQ + \overli...
In the TTL circuit in Figure 2.11, $${S_0}$$ to $${S_0}$$ are select lines and $${X_7}$$ and $${X_0}$$are input lines. $${S_0}$$ and $${X_0}$$ are LSB...
For a binary half-sub-tractor having two inputs A and B, the correct set of logical expressions for the outputs D (=A minus B) and X (=borrow) are

## Marks 5

The inputs to a digital circuit shown in Figure 9(a) are the external signals A, B and C. ( $$\overline A \,\overline B \,and\,\overline {C\,}$$ an...

## Marks 8

The circuit diagram of a 2 bit A to D converter is shown in figure below. The combinational logic is to be disigned to provide a natural binary repres...

## Marks 10

A ROM is to be used to implement the Boolean functions given below: $${F_1}$$$$(A,\,B,\,C,\,D) = ABCD + \bar A\,\overline B \,\bar C\,\bar D$$ $${F_... A Boolean function, F , given as sum of product (SOP) terms as F=$$\sum {} $$m(3,4,5,6) with A,B, and C as inputs. The function, F, can be expreeed o... Signals A,B,C,D and$$\overline D $$are available. Using a single 8 - to - 1 multiplexer and no other gate, implement the Boolean function.$$f(A,B,C...
A chemical reactor has three sensors indicating the following conditions:- (1) Pressure (P) is low or high' (2) Temperature (T) is low or high' and ...
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