The 555 is an integrated circuit first introduced by Signetics, but now produced by many semiconductor manufacturers. The usual package is an 8-pin DIL. Internally the 555 is DC coupled. It can be used for monostable and astable oscillators. The internal construction of the 555 is as follows:
The 555 IC may be used to form an astable oscillator:
The 555 IC may also be used as a monostable:
