Flip-Flops

 

A flip flop is a sequential circuit, with two stable states, that is used to store binary data. The data that is stored can be changed by any changes in the inputs. Flip-flops are sometimes said to be edge-triggered because the edge of the clock signal triggers the flip-flop. Edge-triggering is a beneficial and essential characteristic because it helps circuit designers to get better control over the timing in circuits that contain a large number of flip-flops.

Flip-flops and latches are the fundamental building blocks of digital systems. Flip-flops and latches are both used as data storage elements. These are the basic storage elements in sequential logic. But they have some difference between them. 

Different Types of Flip Flops

We have various types of Flip Flops. They can be categorized as:

• SR flip flop
• D flip flop
• JK flip flop
• T flip flop

SR Flip Flop

SR flip flop is the most common flip flop among all. Just as the SR latch, SR flip flop circuit has a set input (S) and a reset input (R). In SR flip flop, if we Set “S” as active the output “Q” is high, and “ Q‘ ” will be low. Once the outputs are established, the wiring of the circuit is maintained until “S” or “R” go high, or power is turned off. Here is the symbol of SR Flip flop. 

We can easily and simply understand SRs flip flop. Given below is the logic diagram of SR Flip Flop.

The two outputs, as shown in the symbol and logic diagram, are the inverse of each other. The truth table of SR Flip Flop is given below.

JK Flip-flop

Due to the undefined state in the SR flip flop, another flip flop is required in electronics. The JK flip flop is an improvement on the SR flip flop where S=R=1 is not a problem.

The input condition of J=K=1, gives an output inverting the output state. However, the outputs are the same when one tests the circuit practically.

In simple words, If J and K data input are different (i.e. high and low) then the output Q takes the value of J at the next clock edge. If J and K are both low then no change occurs. If J and K are both high at the clock edge then the output will toggle from one state to the other. JK Flip Flop can function as Set or Reset Flip flop

D Flip Flop

D flip flop is a better alternative that is very popular with digital electronics. They are commonly used for counters and shift-registers and input synchronisation.

In a D flip flop, the output can be only changed at the clock edge, and if the input changes at other times, the output will be unaffected.

The change of state of the output is dependent on the rising edge of the clock. The output (Q) is same as the input and can only change at the rising edge of the clock.

T Flip Flop

A T flip flop is like JK flip-flop. These are basically a single input version of JK flip flop. This modified form of JK flip-flop is obtained by connecting both inputs J and K together. This flip-flop has only one input along with the clock input.

These flip-flops are called T flip-flops because of their ability to complement its state (i.e.) Toggle, hence the name Toggle flip-flop.

Applications of Flip-Flops

These are the various types of flip-flops being used in digital electronic circuits and the applications of Flip-flops are as specified below.

Counters

Frequency Dividers

Shift Registers

Storage Registers