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Flip-flop (electronics)

technology Maturity 9-11 Next article →

A flip-flop is a very important part of digital electronics. It acts as a tiny piece of memory that can store one bit of data. A bit is just a single piece of information. It is represented as either a one or a zero.

SR Flip-flop Diagram
SR Flip-flop Diagram

These circuits are called bistable multivibrators. This means they have two stable states. They stay in one state until a signal tells them to change. This ability to hold information makes them the basic building blocks for computers and communication systems.

R-S mk2
R-S mk2

To understand how it works, look at the SR latch. The S stands for set and the R stands for reset. You can build this using two logic gates, like NOR or NAND gates. These gates are connected in a special way called cross-coupling. This means the output of one gate is fed back into the input of the other.

SR NOR Latch How to Work Ver2 20251008
SR NOR Latch How to Work Ver2 20251008

When you send a set signal, the circuit moves to a state of one. When you send a reset signal, it moves to zero. If you send no signal, the circuit simply holds its current state. However, if you try to set and reset at the same time, it enters a forbidden state.

SR Flip-flop Diagram
SR Flip-flop Diagram

People have been working with these circuits for a long time. The first electronic latch was invented in 1918. Two British physicists named William Eccles and F. W. Jordan created it. They used vacuum tubes to make the circuit work.

Eccles-Jordan trigger circuit flip-flip drawings
Eccles-Jordan trigger circuit flip-flip drawings

Later, this design was used in the British Colossus computer in 1943. As technology changed, engineers moved from vacuum tubes to transistors and logic gates. Today, many different types of these circuits are built into single tiny chips.

There are several different types of these storage elements. You might hear names like D, T, or JK flip-flops. Some engineers use the word "latch" for circuits that react to a steady level of signal. They use the word "flip-flop" for circuits that only change when a clock signal hits an edge.

JK timing diagram
JK timing diagram

For example, the 74HC75 is a chip that contains four transparent latches. In 1954, a teacher named Montgomery Phister discussed several types in a UCLA course. He also wrote a book about the logical design of digital computers. Another engineer, Eldred Nelson, helped name the JK flip-flop while working at Hughes Aircraft.

These small circuits are everywhere in our modern world. They allow computers to perform complex tasks by keeping track of many bits at once. They can also be used for counting pulses or helping signals stay in time with a clock.

D-Type Flip-flop Diagram
D-Type Flip-flop Diagram

You can think of them as the tiny switches that allow a computer to remember what it just did. Without these small bits of memory, a computer could not follow a set of instructions. They turn simple electrical signals into the smart machines we use every day.

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🖼️ Images & Media (25)
File:Transistor Bistable interactive animated-en.svg
Transistor Bistable interactive animated-en.svg
File:Eccles-Jordan trigger circuit flip-flip drawings.png
Eccles-Jordan trigger circuit flip-flip...
File:TTL flip-flop.svg
TTL flip-flop.svg
File:R-S mk2.gif
R-S mk2.gif
File:SRLatch-lowres.gif
SRLatch-lowres.gif
File:SR NOR Latch How to Work Ver2 20251008.png
SR NOR Latch How to Work Ver2 20251008.png
File:SR Flip-flop Diagram.svg
SR Flip-flop Diagram.svg
File:Inverted SR latch symbol.png
Inverted SR latch symbol.png
File:RS-and-or-flip-flop.png
RS-and-or-flip-flop.png
File:NAND Gated SR Latch.svg
NAND Gated SR Latch.svg
File:SR (Clocked) Flip-flop Diagram.svg
SR (Clocked) Flip-flop Diagram.svg
File:Gated SR flip-flop Symbol.svg
Gated SR flip-flop Symbol.svg

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