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    The 555 timer IC is an integrated circuit (chip) used in a variety of timer, pulse generation and oscillator applications. The IC design was proposed in 1970 by Hans R. Camenzind and Jim Ball. After prototyping, the design was ported to the Monochip analogue array, incorporating detailed design by Wayne Foletta and others from Qualidyne Semiconductors.

     

    http://uk.farnell.com/productimages/farnell/standard/42268233.jpgSignetics (later acquired by Philips) took over the design and production, and released the first 555s in 1971. The full part numbers were NE555 (commercial temperature range, 0 °C to +70 °C) and SE555 (military temperature range, −55 °C to +125 °C). As with most parts of the era, these were available in both high-reliability metal can (T package) and inexpensive epoxy plastic (V package) packages. Thus the full part numbers were NE555V, NE555T, SE555V, and SE555T.

     

    It has been hypothesized that the 555 got its name from the three 5 resistors used within, but Hans Camenzind has stated that the number was arbitrary. The part is still in widespread use, thanks to its ease of use, low price and good stability. As of 2003, it is estimated that 1 billion units are manufactured every year. The circuit arrangement of the 555 is said to be even more common, being incorporated in thecharge pump of many single-voltage Flash and other electrically-erasable ICs.

     

    Source: http://en.wikipedia.org/wiki/555_timer_IC