Glossary / Semiconductors
Flip-flop
A circuit that stays in one of two stable states and switches to the other when signalled. The smallest component that can remember one bit.
In 1918 William Eccles and Frank Jordan connected two vacuum tubes so that the output of each held the other down[1]. If one is on the other is off, and the circuit stays that way. A brief signal from outside swaps them over.
Computation needs somewhere to keep intermediate results. The flip-flop is the smallest unit of that remembering. Circuits built from transistors on the same principle are still used in vast numbers inside today's chips, holding values in mid-calculation and serving as fast memory.
Related terms
- Vacuum tubeA device that controls a flow of electrons inside an evacuated glass tube. Before the transistor, it did the work of amplifying and switching.
- TransistorA semiconductor device in which a small signal controls a larger current, so it can amplify or switch. The basic component of all electronics.
- DRAMA memory cell that stores one bit as charge on a capacitor. Simple and cheap to make, it serves as the main memory of computers.
On the timeline
Sources
- W. H. Eccles, F. W. Jordan, “A trigger relay utilizing three-electrode thermionic vacuum tubes,” The Radio Review 1, 143–146 (1919).