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555 Timer

555 Timer.svg


The 555 timer is a popular integrated circuit that can do a whole lot in a very small package. Integrated circuits like the 555 hide their complex internal circuits behind a plastic case and have small metal leads to let you hook components up to them.


All ICs have a tiny notch on one side which indicates where pin 1 is on the chip. Pin order is then ascends counter clockwise. Each pin on the IC has a specific function which is exhaustively documented in the IC's datasheet.


Modes of Operation#

  • Astable — has, well, no stable state and the output continually switches between HIGH and LOW.
  • Monostable — output stays in a LOW state until there is a trigger input.
  • Bistable (aka Schmitt Trigger) —

Learn the ins and outs of the 555 timer with the new Patchr: 555 Timer Deep Dive.

IC History

Hans Camenzind invented the 555 timer in 1971 for the American company Signetics Corporation, now a part of Philips.

Patchr Symbol#

555 Timer.svg

Schematic Symbol#

Additional Resources#