555 timer IC

555 timer IC

NE555 from Signetics in 8-pin DIP package
Type	Active, Integrated circuit
Invented	Hans Camenzind
First production	1971
Pin configuration	GND, TRIG, OUT, RESET, CTRL, THR, DIS, VCC
Electronic symbol
Internal block diagram

The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation, and oscillator applications. The 555 can be used to provide time delays, as an oscillator, and as a flip-flop element. Derivatives provide two or four timing circuits in one package.

Introduced in 1972 by Signetics, the 555 is still in widespread use due to its low price, ease of use, and stability. It is now made by many companies in the original bipolar and in low-power CMOS. As of 2003^[update], it was estimated that 1 billion units were manufactured every year. The 555 is the most popular integrated circuit ever manufactured.

The IC was designed in 1971 by Hans R. Camenzind under contract to Signetics (later acquired by Philips Semiconductors, and now NXP).

In 1962, Camenzind joined PR Mallory's Laboratory for Physical Science in Burlington, Massachusetts. He designed a pulse-width modulation (PWM) amplifier for audio applications, but it was not successful in the market because there was no power transistor included. He became interested in tuners such as a gyrator and a phase-locked loop (PLL). He was hired by Signetics to develop a PLL IC in 1968. He designed an oscillator for PLLs such that the frequency did not depend on the power supply voltage or temperature. However, Signetics laid off half of its employees, and the development was frozen due to a recession.

Camenzind proposed the development of a universal circuit based on the oscillator for PLLs, and asked that he would develop it alone, borrowing their equipment instead of having his pay cut in half. Other engineers argued the product could be built from existing parts, but the marketing manager bought the idea. Among 5xx numbers that were assigned for analogue ICs, the special number "555" was chosen.