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Question

In D flip-flop, if D = 1, then the output of the D flip-flop is ______, but if D = 0, then the output of D flip-flop goes to ______ state.

The correct answer is

1; 0

Understanding D Flip-Flop Operation

A D flip-flop is a basic type of sequential logic circuit that stores a single bit of data. Its primary function is to delay the data signal by one clock cycle. The output of the D flip-flop at the next clock edge, denoted as Q(next), is determined solely by the input D at the current clock edge.

D Flip-Flop Behavior Based on D Input

The operation of a D flip-flop is quite straightforward. Let's look at how the output behaves for different inputs:

  • If D = 1: When the D input is high (logic 1) at the time of the active clock edge (usually the rising or falling edge, depending on the design), the D flip-flop captures this logic 1. The output Q will transition to or remain at the high state (logic 1) after the clock edge. This state is often referred to as the 'set' state for the Q output.
  • If D = 0: When the D input is low (logic 0) at the time of the active clock edge, the D flip-flop captures this logic 0. The output Q will transition to or remain at the low state (logic 0) after the clock edge. This state is often referred to as the 'reset' or 'clear' state for the Q output.

In simple terms, the D flip-flop copies the D input to its Q output upon the arrival of a clock pulse.

Truth Table for D Flip-Flop

The behavior of the D flip-flop can be summarized in a simple truth table:

Clock D Input Q (Next State)
Active Edge 0 0
Active Edge 1 1

This table clearly shows that the next state Q is always equal to the current D input.

Analyzing the Question

The question asks for the output states based on the D input:

  • "if D = 1, then the output of the D flip-flop is ______" - Based on the truth table and explanation, if D=1, the next output Q is 1.
  • "but if D = 0, then the output of D flip-flop goes to ______ state." - Similarly, if D=0, the next output Q goes to the 0 state.

Therefore, the correct sequence of outputs is 1 (when D=1) and 0 (when D=0).

Revision Table: Key Flip-Flop Concepts

Term Description
Flip-flop A sequential logic circuit that stores one bit of information.
D Flip-flop A type of flip-flop where the output Q follows the input D after a clock edge.
Clock Signal A periodic signal that controls when the flip-flop changes its state.
Sequential Logic Circuits whose output depends on both current inputs and previous outputs (state).

Additional Information: D Flip-Flop Applications

D flip-flops are fundamental building blocks in digital systems. They are widely used for:

  • Data Storage: Temporarily holding data bits.
  • Registers: Creating parallel registers to store multiple bits.
  • Shift Registers: Moving data bit by bit.
  • Counters: Designing various types of counters.
  • Synchronizing Signals: Aligning data signals with a system clock.

Their simple operation makes them essential components in processors, memory circuits, and control systems.

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Important Questions from Flip-Flop

  1. What is the characteristic of a master-slave flip-flop?

  2. The basic building block of sequential logic circuit is-

  3. For a JK Flip‐flop

    A. When J = 0, K = 1, Q n+1 = 0

    B. When J = 1, K = 1, Q n+1 = 1

    C. When J = 1, K = 1, Q n+1 =\(\rm \overline{Q_n}\)

    D. When J = 1, K = 0, Q n+1 = 1

    E. When J = 1, K = 0, Q n+1 = 0

    Choose the correct answer from the options given below:

  4. In a JK flip flop, if J = K, then resulting flip flop is ______.

  5. Which of the following statements about the T-type flip-flop is correct?

    I. If T = 1, Changes the state of the lining clock pulse.

    II. If T = 0, the state does not change. 

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