555 timer IC

555 timer IC

One of the most versatile linear ICs is the 555 timer which was first introduced in early 1970 by Signetic Corporation giving the name as SE/NE 555 timer. The 555 is a monolithic timing circuit that can produce accurate and highly stable time delays or oscillation. Like general-purpose op-amps, it is very much reliable, easy to use and cheaper in cost. It has a variety of applications including monostable and astable multivibrators, dc-dc converters, digital logic probes, waveform generators, analog frequency meters and tachometers, temperature measurement and control devices, voltage regulators etc. The timer basically operates in one of the two modes either as a monostable (one-shot) multivibrator or as an astable (free-running) multivibrator.The SE 555 is designed for the operating temperature range from – 55°C to 125° while the NE 555 operates over a temperature range of 0° to 70°C.

The important features of the 555 timer are :

  • It operates from a wide range of power supplies (+ 5 V to + 18 V supply voltage).
  • Sinking or sourcing 200 mA of load current.
  • Proper selection of only a few external components allows timing intervals of several minutes or frequencies as high a several hundred kHz.
  • It has a high current output; the output can drive TTL.
  • It has a temperature stability of 50 parts per million (ppm) per degree Celsius change in temperature, or equivalently 0.005 %/ °C.
  • It has an adjustable duty cycle; the maximum power dissipation per package is 600 mW and its trigger and reset inputs are logic compatible.