Electronics Projects: How to Build a D Flip-Flop Circuit - dummies

Electronics Projects: How to Build a D Flip-Flop Circuit

By Doug Lowe

A D flip-flop electronic circuit has just one input in addition to the CLOCK input. This input is called the DATA input. When the clock is triggered, the Q output is matched to the DATA input. Thus, if the DATA input is HIGH, the Q output goes HIGH, and if the DATA input is LOW, the Q output goes LOW.

Most D-type flip-flops also include S and R inputs that let you set or reset the flip-flop. Note that the S and R inputs in a D flip-flop ignore the CLOCK input. Thus, if you apply a HIGH to either S or R, the flip-flop will be set or reset immediately, without waiting for a clock pulse.

This project shows you how to use a 4013 IC to create a basic D flip-flop. This circuit works much the same as the D-type latch. However, it requires only one IC rather than two, and the wiring is much simpler.

That’s because the engineers who designed the 4013 IC crammed all the wiring between the individual NAND gates in the IC, so you don’t have to wire the gates together on the breadboard. Instead, all you have to do is hook up the inputs and the outputs and watch the circuit work.


When you use one of the flip-flops in a 4013 IC, be sure to connect any unused inputs to ground. All unused inputs in CMOS logic chips should be connected to ground, but for simple breadboard circuits, the ground connections aren’t usually required. However, the DATA and CLOCK inputs of a 4013 flip-flop won’t work properly if you don’t ground the SET and RESET inputs.