Fig.1: this is the standard circuit for a monostable using a 555.

When it was first introduced by Signetics back in the early 70s, the 555 seemed like a solution looking for a problem. Given the job of producing a circuit for it back then, as I worked for "Electronics Australia", I racked my brains until I came up with a photo-timer (published in May 1973).

Now, it seems inconceiv­able that such a versatile device as the 555 could have been regarded in this way. It is now acknowledged by many as one of the most successful ICs, perhaps only equalled in fame by the 741 op amp.

The success of the 555 can be attributed to its flexibili­ty, performance and its ability to satisfy the timing require­ments of a huge number of applications. Over the years the origi­nal 555 has been supplemented by CMOS versions which operate on much lower current and at lower voltage.

The new 555 timer from Zetex takes the performance to the next level – operation from a single cell, guaranteed operation down to 0.9V and bipolar technology.