Many electronic circuits frequently 205 require the brief delay of a pulse. Such a delay, here between 100 ps and 100 s, is easily provided by a simple circuit based on the popular 555. That is more than adequate for most applications. The output of the 555 can go high only if the potential at pin 2 drops below a third of the level of the supply voltage, provided that the level at pin 4 is high. In quiescent operation, the level at pin 4 is low and C1 is charged via T1 so that the output is low. Then the input goes high, Ti is switched off and C1 is discharged via R1. In that con-uni on, the reset state is canceled, and alter a time delay that depends on the state of discharge of C1 the output of the 555 goes high. The time delay in seconds is calculated from t = 0.69R14C1, where R1 must be greater than or equal to 10 kΩ.
555 Timer Output
A collection of 555 circuits using the 555 Timer as an astable oscillator with different duty cycles.
The standard TTL 555 can operate from a supply voltage between 4.5 volts and 18 volts, with its output voltage approximately 2 volts lower than its supply voltage VCC. The 555 can source or sink a maximum output current of 200mA, (but it may get hot at this level), so the circuit variations are unlimited. Note that the CMOS versions of the 555, the 7555, and the 7556 may have different voltage and current ratings.
