Pin 3: Output: It's the output which responds to the input pins either by going high or low, or by oscillating ON/OFF.This ON/OFF switching is done by an internal FLIP-FLOP stage. The capacitor then slowly charges via the timing resistor, and when it rises above 2/3rd supply level, pin3 become LOW again. This happens by a quick discharging of the timing capacitor below the lower threshold level of 1/3rd supply voltage. Pin 2: Trigger or input: A negative momentary trigger on this input pin causes the output pin3 to go HIGH.Pin 1: Ground or 0V: It's the negative supply pin of the IC.You will also find the CMOS version of timer known as 7555 and TLC555 these consume less power compared to standard 555 and operate less than 5V.ĬMOS version timers consist of MOSFETs rather than bipolar transistor, which is efficient and consume less power. The SE555 is military grade IC and has operating temperature range of -55 to +125 degree Celsius. The NE555 is a civilian grade IC and has operating temperature range of 0 to +70 degree Celsius. There are two versions of the IC available namely military and civilian grade 555 timer. How IC 555 WorksĪ standard IC555 consist of 25 transistors, 15 resistors and 2 diodes integrated on a silicon die. However, some hypothesis claims that the selection of the name has no relation to the internal components of the IC, it was arbitrarily selected. If we look at the internal block diagram of IC 555 we find three 5K ohm resistors connected in series for deciding the timing factor, so probably that's how the device got its name IC 555 timer. The Signetics Company is owned by Philips Semiconductor. That’s one IC 555 for every 7 people in the world. It is estimated that about 1 billion IC 555s are manufactured every year. IC 555 was introduced in 1971 by a company called “Signetics” it was designed by Hans R. In this article we are going to look back at history of IC555, their 3 operating modes and some of their specifications.

It would be one of our first IC to use in electronics. Our hobby world would be less interesting without IC 555.

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