D Flip Flop in Digital Electronics

Last Updated on October 26, 2023 by Electricalvolt

The D flip flop is the most important flip flop in digital electronics. The both inputs of the flip flop. S & R, can never be equal one at the same time. To get this , we use a gated SR FF with an inverter between the inputs.

In digital electronics, a flip flop is a logic circuit that is used to store 1 bit of binary information. Therefore, the flip-flops are considered fundamental building block of digital storage devices.

Based on construction and design, several different types of flip-flops(FFs) are available such as SR , JK, T , and D FF. In this article, we will discuss D FF, its truth table, circuit diagram, and applications.

What is a D Flip Flop?

The D flip flop have only one input line D and two output lines Q and Q’. It also has a clock input line for triggering of the circuit.

The logic block diagram is shown in the following figure.

logic block diagram of a D flip flop

Here, it has an input line designated by the symbol D, where a binary input is applied. Another input line to the D FF is a clock signal, denoted by CLK. The signal is utilized to synchronize and trigger the flip-flop. The output Q is the normal output which determines the state of the flip-flop, while the output Q’ is the complemented output which is inversion of the normal output Q.

D Flip Flop Circuit Diagram

We can design a D FF using digital logic gates. The logic circuit diagram of a D flip-flop is shown below.

D Flip Flop Circuit Diagram

It is clear that we can design a D flip-flop by using five NAND gates. It is basically a NAND logic SR FF in which S is directly connected to D input and the R is connected to the D input through an invert gate.

Truth Table of D Flip-Flop

Truth table provides information about its operation for different values of input D. The truth table of D FF is shown in the below table.

Input (D)Next State (Qn+1)Comment

From the truth table of D flip-flop, it is clear that when the value of the input D is logic 0, the D FF enters to the reset state, and when the input D is logic 1, the FF goes into the set state.

Characteristic Table of D Flip-Flop

The characteristic table of a D FF provides information about transition of state as per the input signal. The characteristic table is given below:

Input (D)Previous State (Qn)Next State (Qn+1)

Characteristic Equation of D Flip Flop

We can use K-Map and characteristic table of D FF to derive its characteristic equation.

The K-map simplification of the characteristic table is shown below.

 K-map simplification of the characteristic table of D flip-flop

From the K-map simplification, we get the following expression as the characteristic equation.

 characteristic equation of D flip-flop.


The following are some major advantages of D flip flop.

  • It is simpler to design and use in digital circuits, as it has only one input line.
  • It does not have the problem of race condition due to absence of feedback loop.
  • It does not have any invalid state.
  • It consumes less power.


Some common applications of D FF are listed below:

  • Used in shift registers in digital systems.
  • Used to introduce a delay in a digital system.
  • Also used to design state machines.
  • For designing binary counters.

This is all about D flip-flop, its truth table, and applications. The D FF is a very simple circuit used to store binary information in digital systems.

Please follow and like us:
About Ayushi

Ayushi is B.Tech in Electronics & Communication engineering from National Institute of Technology(NIT-Surat). She has 4 years of experience, and her area of interest is power electronics, digital electronics, artificial intelligence and data science.

Your subscription could not be saved. Please try again.
Your subscription has been successful.

Want To Learn Faster?

Get electrical, electronic, automation, and instrumentation engineering articles delivered to your inbox every week.

Leave a Comment