Flip-Flops

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Definition

It is circuit that consists of memory element which can store one binary digit i.e. bit, this memory element is called as flip-flop.

Description

Flip-flops are constructed by a pair of cross-coupled inverting elements like logic gates, invertors, transistors etc. Have normally complimentary outputs and can maintain a stable output even after the inputs are turned off. This concept of storing a bit gave rise to RAM (Random Access Memory) and other useful circuits.

Types

S-R flip-flop

• S and R stands for Set and Reset flip-flop.
• Constructed by a pair of cross-coupled NAND or NOR gates.
• When S and R are 0, there is no change and remains in same state.
• When S = 0 and R = 1 then Q output is low(0) and stays low even after R returns 0.
• When S = 1 and R = 0 then Q output is high(1) and stays high even after S return 0.
• S and R = 1 is not aloud because both output Q and Q' tries to become 1, this condition called as Race condition.

J-K flip-flop

• Eliminates the race condition of S-R Flip-flop when S and R = 1.
• Constructed by using NAND gates and clock.
• When both input J and K = 0 there is no change in the state.
• When J and K are different then Q takes the value of J.
• When J And K are high then outputs toggles from one state to another.

D-type flip-flop

• It has only one input referred as data input.
• Constructed by connecting J-K or S-R flip to S or J = D and R or K = not D and a clock.
• Input data appears as it is at the output end.
• Thus transfer of data from the input to the output is delayed.
• Hence the name delay flip-flop.
• Used as a delay device or latch to store 1 bit binary information.

T-type flip-flop

• It has only one input refferred as T-input.
• Constructed by connecting J-K flip-flop and a clock.
• In J-K flip flop, if J = K the resulting flip-flop called as T type flip-flop.
• It acts as toggle switch.

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