Scheme – I

# Sample Question Paper

 Program Name : Electronics and Computer Engineering Program Group Program Code : CO/CM/CW/DE/EJ/ET/EN/EX/IE/IS/IC/MU Semester          Course Title    70Marks : Third  : Digital Techniques

## Q.1) Attempt any FIVE of the following.                                                             10 Marks

a)       Write the base of the following number systems: Decimal, Binary, Octal, and Hexadecimal.
b)       Draw symbol and write the truth table of JK flip flop.
c)       State the necessity of multiplexer.
d)       Write excitation table of D flip flop.
e)       List any two specifications of IC- DAC 0808.
f)        Draw three variable K-map format.
g)       Define modulus of a counter? Write down the number of flip flops required for mod-5 counter?

## Q.2) Attempt any THREE of the following.                                                         12 Marks

a)              For the given figure No. 1, derive the Boolean expression of Y.

Figure No. 1
b)             Draw the circuit diagram of BCD to 7 segment decoder and write its truth table.
c)              Draw the block diagram of Programmable Logic Array.
d)             Minimize the following expression using K-map.
f (P, Q, R, S) = Ξ£ m (0, 1, 4, 5, 7, 8, 9, 12, 13, 15).

## Q.3) Attempt any THREE of the following.                                                         12 Marks

a)       Realize the following logic operations using only NAND gates: AND, OR, NOT.
b)       Compare TTL and CMOS logic families on the basis of following:
i) Propogation delay ii) Power dissipation iii) Fan-out iv) Basic gate
c)       Describe the operation of 4- bit universal shift register with the help of block diagram.
d)       Calculate analog output of 4 bit DAC for digital input is 1011. Assume VF S= 5V.

## Q.4) Attempt any THREE of the following.                                                         12 Marks

a)       Draw the symbol and write logic expression and truth table of the two input universal logic gates.
b)       Describe function of full subtractor circuit with its truth table, K-map simplification and logic diagram.
c)       Design 1: 16 demultiplexer using 1: 4 demultiplexers.
d)       Describe the working of Master-Slave JK Flip-Flop with Truth Table and Logic diagram.
e)       The output of 8 bit DAC varies between +10V and -10V. Calculate the following:
i) Resolution   ii) Percentage resolution.

## Q.5) Attempt any TWO of the following.                                                             12 Marks

a)       Design 3-bit synchronous counter and draw output waveform.
b)       Compare the following (Any three points)             .
(i)    Volatile with Non-Volatile memory.
(ii)  SRAM with DRAM memory.
c)       Convert the following :
(i)    (5C7)16 = (?)10 ii) (2598)10 = (?)16 iii) (10110)2 = (?)10 = (?)16

## Q.6) Attempt any TWO of the following.                                                             12 Marks

a)                 Describe the procedure to design MOD-6 counter using IC 7490 in brief.
b)                Design a four bit BCD adder using IC 7483 and NAND gates only.
Identify the circuit shown as figure no.2 and explain its working.