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Test 4 - Digital Circuits | Electronics and Communication (ECE)

Topic wise test for Digital Circuits of Electronics and Communication (ECE)

15 Questions Published
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Questions

Question 1 Multiple Choice (Single Answer)

The following binary values were applied to the X and Y inputs of the NAND latch shown in the figure in the sequence indicated below:
X = 0, Y = 1; X = 0, Y = 0; X = 1, Y = 1.
The corresponding stable P, Q outputs will be

  1. P = 1, Q = 0; P = 1, Q = 0; P = 1, Q = 0 or P = 0, Q = 1
  2. P = 1, Q = 0; P = 0, Q = 1; or P = 0, Q = 1; P = 0, Q = 1
  3. P = 1, Q = 0; P = 1, Q = 1; P = 1, Q = 0 or P = 0, Q = 1
  4. P = 1, Q = 0; P = 1, Q = 1; P = 1, Q = 1
Question 2 Multiple Choice (Single Answer)

For the circuit shown below, the counter state (Q1, Q0) follows the sequence

  1. 00, 01, 10, 11, 00 …
  2. 00, 01, 10, 00, 01 …
  3. 00, 01, 11, 00, 01 …
  4. 00, 10, 11, 00, 10 …
Question 3 Multiple Choice (Single Answer)

Figure shows a ripple counter using positive edge triggered flip-flops. If the present state of counter is Q2Q1Q0 = 011, then its next state (Q2Q1Q0) will be

  1. 010
  2. 100
  3. 111
  4. 101
Question 4 Multiple Choice (Single Answer)

In the modulo-6 ripple counter shown in the figure below, the output of the 2- input gate is used to clear the J-K flip-flop. The 2-input gate is

  1. a NAND gate
  2. a NOR gate
  3. an OR gate
  4. an AND gate
Question 5 Multiple Choice (Single Answer)

The Boolean expression AC + $B\bar C$ is equivalent to

  1. $\bar AC + B\bar C + AC$
  2. $\bar BC + AC + B\bar C+\bar A C \bar B$
  3. $AC+B\bar C + \bar B C + ABC$
  4. $ABC + \bar A B \bar C + AB \bar C + A \bar B C$
Question 6 Multiple Choice (Single Answer)

A 4-bit D/A converter is connected to a free-running 3-bit UP counter, as shown in the following figure. Which of the following waveforms will be observed at V0?

Question 7 Multiple Choice (Single Answer)

If the functions W, X, Y and Z are as follows:
W = R + $\bar P Q + \bar RS$
X = PQ$\bar R \bar S + \bar P \bar Q \bar R \bar S + P \bar Q \bar R \bar S$
Y = RS + $\overline{PR + P \bar Q + \bar P \bar Q}$
Z = R + S + $\overline{PQ + \bar P \bar Q \bar R + P \bar Q \bar S}$
then

  1. W = Z, X = $\mathcal{Z}$
  2. W = Z, X = Y
  3. W = Y
  4. W = Y = $\mathcal{Z}$
Question 8 Multiple Choice (Single Answer)

A 0 to 6 counter consists of 3 flip flops and a combination circuit of 2 input gate(s). The combination circuit consists of

  1. one AND gate
  2. one OR gate
  3. one AND gate and one OR gate
  4. two AND gates
Question 9 Multiple Choice (Single Answer)

For the circuit shown in figure below, two 4-bit parallel-in serial-out shift registers loaded with the data shown are used to feed the data to a full-adder. Initially, all the flip-flops are in clear state. After applying two clock pulses, what will be the outputs of the full-adder?

  1. S = 0, C0 = 0
  2. S = 0, C0 = 1
  3. S = 1, C0 = 0
  4. S = 1, C0 = 1
Question 10 Multiple Choice (Single Answer)

Two D-flip-flops, as shown below, are to be connected as a synchronous counter that goes through the following Q1 Q0 sequence
00 $\rightarrow$ 01 $\rightarrow$ 11 $\rightarrow$ 10 $\rightarrow$ 00 $\rightarrow$.........
The inputs D0 and D1 respectively should be connected as

  1. $\bar Q_1$ and Q0
  2. $\bar Q_0$ and Q1
  3. $\bar Q_1$$\bar Q_0$ and $\bar Q_1$ Q0
  4. $\bar Q_1$$\bar Q_0$ and Q0 Q1
Question 11 Multiple Choice (Single Answer)

The DTL, TTL, ECL and CMOS families of digital ICs are compared in the following 4 columns:

(P) (Q) (R) (S)
Fanout is minimum DTL DTL TTL CMOS
Power consumption is minimum TTL CMOS ECL DTL
Propagation delay is minimum CMOS ECL TTL TTL
The correct column is
  1. P
  2. Q
  3. R
  4. S
Question 12 Multiple Choice (Single Answer)

For the circuit shown in the following, I0 - I3 are inputs to the 4 : 1 multiplexers, R (MSB) and S are control bits.
The output Z can be represented by

  1. PQ + P$\bar Q$S + $\overline{QRS}$
  2. P$\bar Q$ + PQ$\bar R$+ $\overline{PQS}$
  3. P$\overline{QR}$+ $\bar P$QR + PARS + $\overline{QRS}$
  4. PQ$\bar R$+ PQR$\bar S$+ P$\overline{QR}$S + $\overline{QRS}$
Question 13 Multiple Choice (Single Answer)

It is desired to multiply the numbers 0AH by 0BH and store the result in the accumulator. The numbers are available in registers B and C respectively. A part of the 8085 program for this purpose is given below :
MVI A, 00H
LOOP ------

HLT
END
The sequence of instructions to complete the program would be

  1. JNX LOOP, ADD B, DCR C
  2. ADD B, JNZ LOOP, DCR C
  3. DCR C, JNZ LOOP, ADD B
  4. ADD B, DCR C, JNZ LOOP
Question 14 Multiple Choice (Single Answer)

Which of the following Boolean Expressions correctly represents the relation between P, Q, R and M1?

  1. M1 = (P OR Q) XOR R
  2. M1 = (P AND Q) X OR R
  3. M1 = (P NOR Q) X OR R
  4. M1 = (P XOR Q) XOR R
Question 15 Multiple Choice (Single Answer)

In the following circuit, X is given by

  1. X = $A\bar B \bar C+ \bar A B \bar C + \bar A \bar B C + ABC$
  2. X = $\bar A BC + A\bar B C + AB\bar C + \bar A \bar B \bar C$
  3. X = $AB + BC+ AC$
  4. X = $\bar A \bar B + \bar B \bar C + \bar B \bar C + \bar A \bar C$
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