DF GTU Paper Solution Winter 2021 | 3130704

Here, We provide Digital Fundamentals GTU Paper Solution Winter 2021. Read the Full DF gtu paper solution given below.

DF GTU Old Paper Winter 2021 [Marks : 70] : Click Here 

Question: 1

(a) Implement EX-NOR using the NAND gate.

  • Block Diagram

(b) Convert the decimal number 225.225 to octal and hexadecimal.

(c) Give a classification of logic families and compare CMOS and TTL.

(a) Convert F(A,B,C) = BC+A into standard minterm form.

(b) With a logic diagram and truth table, explain the working of 3 lines to an 8-line decoder. 

This decoder circuit gives 8 logic outputs for 3 inputs and has a enable pin. The circuit is designed with AND and NAND logic gates. It takes 3 binary inputs and activates one of the eight outputs. 3 to 8-line decoder circuit is also called a binary to an octal decoder.

Logic diagram – 


Truth Table :


(c) Explain the Successive Approximation A/D converter in detail.

(c) A combinational logic is defined by functions: F1(A,B,C) = ∑m (3,5,6,7) F2(A,B,C) = ∑m (0,2,4,7) Implement the circuit with PLA having 3 inputs, 4 product terms & 2 outputs.

(a) Simplify the Boolean expression: F(x,y,z) = ∑m (0,1,3,4,5,7) 

(b) Explain S-R clocked flip flop.

An S-R (Set-Reset) Clocked Flip-Flop is a type of Flip-Flop that uses two inputs, S (set) and R (reset), and a clock input to control the state of the flip-flop. The flip-flop is a synchronous circuit, meaning that the state of the flip-flop changes only when a clock signal is applied.

  • Block Diagram

The working of an S-R Clocked Flip-Flop can be described as follows:

When a rising edge of the clock signal is applied, the inputs S and R are latched and the state of the flip-flop is determined.

  • If both S and R are at logic low, the state of the flip-flop does not change, and it remains in its previous state.
  • If S is at logic high and R is at logic low, the output Q is set to logic high and the output Q’ is set to logic low. This is known as the set state.
  • If S is at logic low and R is at logic high, the output Q is set to logic low and the output Q’ is set to logic high. This is known as the reset state.
  • If both S and R are at logic high, the flip-flop is in an undefined state and the output is unpredictable.

(c) Design a full adder circuit using a decoder and multiplexer.


(a) Generate AND & EX-OR gates using NOR gate.

  • AND gate using NOR Gate.
  • EX-OR Gate using NOR Gate.

(b) Implement D flip flop using JK flip flop.

(c) Design a counter to generate the repetitive sequence 0,4,2,1,6.

(a) What is the race-around condition in JK flip flop?

A race-around condition in a J-K Flip-Flop is a phenomenon that occurs when the J and K inputs change state simultaneously and both inputs are at logic level 1. In this condition, the output of the Flip-Flop will change state twice before the clock pulse ends, thus creating an unstable output. This is known as a race-around condition.

To avoid a race-around condition, it is recommended to use a pulse generator circuit that ensures that the J and K inputs are never at logic high at the same time.

(b) Construct a ring counter with five timing signals. 

(c) Design BCD to Excess 3 code converters using a minimum number of NAND gates.


(a) Explain the 2-bit comparator circuit. 

A 2-bit comparator circuit is a digital circuit that compares two 2-bit binary numbers and produces a signal indicating which number is greater, equal or less than the other. The comparator circuit typically has 2-bit inputs A and B, and several output signals indicating the comparison result.

Block Diagram:


Truth Table: 


(b) Write a short note on FPGA.

(c) What is a Digital to Analog converter? Draw and Explain R-2R DAC.

(a) Perform the following operation using 2’s complement method. (11010)2 – (1000)2

(b) Write a short note on Read Only Memory (ROM).

Read-Only Memory (ROM) is a type of non-volatile memory that stores data permanently and can only be read by a computer or other electronic device. It is called read-only because it can only be read from, not written to.

ROM is used in a wide range of electronic devices such as computers, cell phones, and other embedded systems. It is commonly used to store firmware, which is a set of instructions that control the basic functions of the device. The firmware is written to the ROM during the manufacturing process and cannot be changed or modified by the user.

There are several types of ROM, each with its own unique characteristics and uses. Some common types of ROM include:

  • Mask ROM: which is programmed during the manufacturing process and cannot be reprogrammed afterward.
  • Programmable ROM (PROM): which can be programmed once by the user, but cannot be reprogrammed afterward.
  • Erasable Programmable ROM (EPROM): which can be reprogrammed by the user using ultraviolet light.
  • Electrically Erasable Programmable ROM (EEPROM): which can be reprogrammed by the user using electrical signals.

(c) Explain the working of a 4-bit binary ripple counter.


(a) Obtain the truth table of the function: F = xy+yz+zx.


(b) Implement the following functions using ROM. F1 = ∑m (1,3,4,6) and F2 = ∑m (0,1,5,7). 

(c) Explain in detail the Dual Slope A/D converter.

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