# Sequential Circuit

 Question 1
Consider a 3-bit counter, designed using T flip-flops, as shown below:

Assuming the initial state of the counter given by PQR as 000, what are the next three states?
 A 011,101,000 B 001,010,111 C 011,101,111 D 001,010,000
GATE CSE 2021 SET-1   Digital Logic
Question 1 Explanation:
 Question 2
A new flipflop with inputs X and Y, has the following property
$\begin{array}{|c|c|c|c|} \hline \mathbf{X} & \mathbf{Y} & \text { Current state } & \text { Next state } \\ \hline 0 & 0 & Q & 1 \\ 0 & 1 & Q & \bar{Q} \\ 1 & 1 & Q & 0 \\ 1 & 0 & Q & Q \\ \hline \end{array}$
Which of the following expresses the next state in terms of X,Y, current state?
 A $(\bar{X} \wedge \bar{Q}) \vee(\bar{Y} \wedge Q)$ B $(\bar{X} \wedge {Q}) \vee(\bar{Y} \wedge \bar{Q})$ C $({X} \wedge \bar{Q}) \vee({Y} \wedge {Q})$ D $({X} \wedge \bar{Q}) \vee(\bar{Y} \wedge {Q})$
ISRO CSE 2020   Digital Logic
Question 2 Explanation:
 Question 3
Consider the sequential circuit shown in the figure, where both flip-flops used are positive edge-triggered D flip-flops.

The number of states in the state transition diagram of this circuit that have a transition back to the same state on some value of "in" is _____.
 A 1 B 2 C 3 D 4
GATE CSE 2018   Digital Logic
Question 3 Explanation:
 Question 4
Advantage of synchronous sequential circuits over asynchronous one is :
 A Lower hardware requirement B Better noise immunity C Faster operation D All of the above
ISRO CSE 2017   Digital Logic
Question 4 Explanation:
 Question 5
The next state table of a 2-bit saturating up-counter is given below.
$\begin{matrix} Q_{1} & Q_{0} & Q_{1}^{+} &Q_{0}^{+} \\ 0 & 0 & 0 & 1 \\ 0 & 1 & 1 & 0\\ 1 & 0 & 1 & 1\\ 1 & 1 & 1 & 1 \end{matrix}$
The counter is built as a synchronous sequential circuit using T flip-flops. The expression for $T_1 \; and \; T_0$ are
 A $T_{1}=Q_{1} Q_{0} , \; \; T_{0}=\bar{Q_{1}}\bar{Q_{0}}$ B $T_{1}=\bar{Q_{1}} Q_{0} , \; \; T_{0}=\bar{Q_{1}}+\bar{Q_{0}}$ C $T_{1}=Q_{1} + Q_{0} , \; \; T_{0}=\bar{Q_{1}}+\bar{Q_{0}}$ D $T_{1}=Q_{1} Q_{0} , \; \; T_{0}=\bar{Q_{1}}+\bar{Q_{0}}$
GATE CSE 2017 SET-2   Digital Logic
Question 5 Explanation:
 Question 6
Consider a combination of T and D flip-flops connected as shown below. The output of the D flip-flop is connected to the input of the T flip-flop and the output of the T flip-flop is connected to the input of the D flip-flop

Initailly, both $Q_{0}$ and $Q_{1}$ are set to 1 (before the 1st clock cycle). The outputs
 A $Q_{1}Q_{0}$ after 3rd cycle are 11 and after the 4th cycle are 00 respectively B $Q_{1}Q_{0}$ after 3rd cycle are 11 and after the 4th cycle are 01 respectively C $Q_{1}Q_{0}$ after 3rd cycle are 00 and after the 4th cycle are 11 respectively D $Q_{1}Q_{0}$ after 3rd cycle are 01 and after the 4th cycle are 01 respectively
GATE CSE 2017 SET-1   Digital Logic
Question 6 Explanation:
 Question 7
The functional difference between SR flip-flop and J-K flip-flop is that :
 A J -K flip-flop is faster than SR flip-flop B J-K flip-flop has a feedback path C J-K flip-flop accepts both inputs 1 D None of them
ISRO CSE 2016   Digital Logic
Question 7 Explanation:
 Question 8
We want to design a synchronous counter that counts these quence 0-1-0-2-0-3 and then repeats. The minimum number of J-K flip flop srequired to implement this counteris ________.
 A 3 B 4 C 5 D 2
GATE CSE 2016 SET-1   Digital Logic
Question 8 Explanation:
 Question 9
A modulus -12 ring counter requires a minimum of
 A 10 flip-flops B 12 flip-flops C 8 flip-flops D 6 flip-flops
ISRO CSE 2015   Digital Logic
Question 9 Explanation:
 Question 10
The minimum number of JK flip-flops required to construct a synchronous counter with the count sequence (0,0,1,1,2,2,3,3,0,0,...) is __________ .
 A 2 B 3 C 4 D 5
GATE CSE 2015 SET-2   Digital Logic
Question 10 Explanation:
There are 10 questions to complete.

### 5 thoughts on “Sequential Circuit”

1. please correct Qestion number 8

• Thank You PRAFUL devendra,

2. Update the first question the options are not correct its scrambled

• Thank You Neeraj Hebbar,
We have updated the option

3. Q27 options are wrong..
a option should be 0110