More Applications For The 555

24 EE February 1989 vcc 555/7555/TLC555 MORE APPLICATIONS FOR THE 555 There are probably few integrated circuits that have been with us for as long as timer Type 555. This article does not add to the seemingly endless list of AMV and MMV applications of this chip, but discusses some less familar designs derived from these. In addition, a brief introduction is given to the new CMOS and LinCMOS versions of the 555. One explanation of the popularity of the now 17-year-old timer type 555 may be that the chip is inexpensive, and contains a fairly unique combination of sub- circuits. Looking at the internal struc- ture shown in Fig. 1, these are a bistable (a digital circuit), two comparators (analogue circuits) and some discrete parts, a resistive potential divider and a transistor. Added to the versatility of these interesting building blocks come the abilities of the chip to supply a rela- tively high output current, and to work from a wide range of supply voltages. Pin assignments o...