GATE ECE
Digital Circuits
Sequential Circuits
Previous Years Questions

## Marks 1

for the circuit shown, the clock frequency is f0 and the duty cycle is 25%. For the signal at the Q output of the Flip-Flop, ___________. ...
A state transition diagram with states A, B, and C, and transition probabilities p1, p2, ....., p7 is shown in the figure (e.g., p1 denotes the prob...
A traffic signal cycles from GREEN to YELLOW, YELLOW to RED and RED to GREEN. In each cycle, GREEN is turned on for 70 seconds, YELLOW is turned on fo...
Consider the D-Latch shown in the figure, which is transparent when its clock input CK is high and has zero propagation delay. In the figure, the cloc...
In the latch circuit shown, the NAND gates have non-zero, but unequal propagation delays. The present input condition is: P = Q = "0‟. If the input co...
Assume that all the digital gates in the circuit shown in the figure are ideal, the resistor 𝑅 = 10 𝑘Ω and the supply voltage is 5 𝑉. The D flip-fl...
A mod-n counter using a synchronous binary up-counter with synchronous clear input is shown in the figure. The value of n is _______. ...
The circuit shown consists of J-K flip-flops, each with an active low asynchronous reset ($$\overline {{R_d}}$$ input). The counter corresponding to ...
The circuit shown in the figure is a ...
Consider the multiplexer based logic circuit shown in the figure. Which one of the following Boolean functions is realized by the circuit?...
Five JK flip - flops are cascaded to form circuit shown in figure. Clock pulses at a frequency of 1 MHz are applied as shown. The frequency (in kHz) o...
Consider the given circuit. In this circuit, the race around ...
When the output Y in the circuit below is ‘1’, it implies that data has ...
Assuming that all flip-flops are in reset condition initially, the count sequence observed at QA in the circuit shown is ...
The given figure shows a ripple counter using positive edge triggered flip-flops. If the present state of counter is Q2 Q1 Q0 = 011, then its next st...
The present output Qn of an edge triggered JK flip-flop is logic 0. If J=1, then Qn+1
A master slave flip-flop has the characteristic that
Choose the correct one from among the alternatives A, B, C, D after matching an item from Group 1 with the most appropriate item in Group 2. Group1 P....
A 0 to 6 counter consist of 3 flip-flops and a combination circuit of 2 input gate(s). The combination circuit consists of
Figure shows a mod-K counter, Here K is equal to ...
In a J_K flip-flop, we have J=$$\overline Q$$ and K=1 (see figure). Assuming the flip-flop was intially cleared and then clocked for 6 pulses, the se...
A switch-tail ring counter is made by using a single D flip-flop. The resulting circuit is a
An R-S latch is
Synchronous counters are _____ than the ripple counters.
A pulse train with a frequency of 1 MHz is counted using a modulo-1024 ripple-counter built with J-K flip flops. For proper operation of the counter, ...
The initial contents of the 4-bit serial-in-parallel-out, right-shift, Shift Register shown in figure is 0110. After three clock pulses are applied, t...
A SR FLIP-FLOP can be converted into a T FLIP-FLOP by connecting ___ to Q and ___ to $$\overline Q$$.
A 4 bit modulo-16 ripple counter uses JK flip-flops. If the propagation delay of each FF is 50ns, the maximum clock frequency that can be used is equa...
The circuit given below is a ...
A ripple counter using negative edge-triggered D-flip flops is shown in Fig.1. The flip-flops are cleared to '0' by a '0' at the R input. The feedback...
Choose the correct statements relating to the circuit of figure ...

## Marks 2

In the circuit shown below, a positive edge-triggered D Flip-Flop is used for sampling input data Din using clock CK. The XOR gate outputs 3.3 volts f...
A 4-bit shift register circuit configured for right-shift operation is $${D_{in}}\, \to \,A,\,A\, \to B,\,B \to C,\,C \to D,$$ is shown. If the presen...
A finite state machine (FSM) is implemented using the D flip-flops A and B and logic gates, as shown in the figure below. The four possible states of ...
The state diagram of a finite state machine (FSM) designed to detect an overlapping sequence of three bits is shown in the figure. The FSM has an inpu...
The state transition diagram for a finite state machine with states A, B and C, and binary inputs X, Y and Z, is shown in the figure. Which one of ...
For the circuit shown in the figure, the delay of the bubbled NAND gate is 2ns and that of the counter is assumed to be zero If the clock (Clk) freq...
The figure shows a binary counter with synchronous clear input. With the decoding logic shown, the counter works as a ...
A three bit pseudo random number generator is shown. Initially the value of output Y = Y2 Y1 Y0 is set to 111. The value of output Y after three clock...
An SR latch is implemented using TTL gates as shown in the figure. The set and reset pulse inputs are provided using the push-button switches. It is o...
The outputs of the two flip-flops Q1, Q2 in the figure shown are initialized to 0, 0. The sequence generated at Q1 upon application of clock signal i...
In the circuit shown, choose the correct timing diagram of the output (y) from the given waveforms W1, W2, W3 and W4. ...
The digital logic shown in the figure satisfies the given state diagram when Q1 is connected to input A of the XOR gate. Suppose the XOR gate is re...
The state transition diagram for the logic circuit shown is ...
Two D flip-flops are connected as a synchronous counter that goes through the following QB QA sequence $$00 \to 11 \to 01 \to 10 \to 00 \to ......$$ ...
The output of a 3-stage Johnson (twisted-ring) counter is fed to a digital-to-analog (D/A) converter as shown in the figure below. Assume all the stat...
What are the counting states (Q1, Q2) for the counter shown in the figure below? ...
For each of the positive edge-triggered J-K flip flop used in the following future, the propagation delay is $$\Delta$$T Which of the following wav...
For the circuit shown, the counter state (Q1 Q0) follows the sequence ...
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...
Two D-flip-flops, as shown below, are to be connected as a synchronous counter that goes through the following Q1Q0 sequence $$00 \to 01 \to 11 \to 10... In the modulo-6 ripple counter shown in the figure, the output of the 2-input gate is used to clear the J-K flip-flops. The 2-input gate is ... A 4 bit ripple counter and a 4 bit synchronous counter are made using flip-flops having a propagation delay of 10 ns each. If the worst case delay in ... The digital block in the figure is realized using two positive edge triggered D flip-flops. Assume that for t < t0, Q1 = Q2 =0. The circuit in the ... A sequential circuit using D flip-flop and logic gates is shown in the figure, where X and Y are the inputs and Z is the output. The circuit is ... In the figure, the J and K inputs of all the four Flip-Flops are made high. The frequency of the signal at output Y is ... The ripple counter shown in the figure works as a ... In figure, A = 1 and B = 1. The input B is now replaced by a sequence 101010 ___, the outputs x and y will be ... ## Marks 5 It is required to design a binary mod-5 synchronus counter using AB flip-flops such that the output Q2Q1Q0 changes as$$000 \to 001 \to 010 ........
The circuit diagram of a synchronous counter is shown in the figure. Determine the sequence of states of the counter assuming that the initial state i...
The mod-5 counter shown in figure counts through states Q2 Q1 Q0 = 000, 001, 010, 011 and 100. (a) Will the counter lockout if it happens to be in...
A sequence generator is shown in figure. The counter status (Q0 Q1 Q3) is intialized to 010 using preset/clear inputs. The Clock has a period of 50ns ...
A 4-bit shift register, which shifts 1 bit to the right at every clock pulse, is intialized to values (1000) for (Q0Q1Q2Q3). The D input is derived fr...
A state machine is required to cycle through the following sequence of states: One possible implementation of the state machine is shown figure. Spe...

## Marks 8

A new clocked "X-Y" flip-flop is defined with two inputs, X and Y in addition to the clock input. The flip-flop functions as follows: If XY=00, the fl...
The circuit shown below uses TTL flip-flops. The flip-flops are triggered at the negative transitions of the clock. It is desired that when M = 1 the ...
For the circuit shown in the figure below, sketch V0 against time. Assume that all flip-flops are reset to zero before the clock is applied. ...
A 2-input up/down synchrconous counter using two toggle flip-flops is shown in Fig.1. The counter's sequence is to be controlled by the input M as fol...
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