Inside the 555

Note: Pin 7 is "in phase" with output Pin 3 (both are low at the same time).
Pin 7 "shorts" to 0v via a transistor. It is pulled HIGH via R1.
Maximum supply voltage 16v - 18v
Current consumption approx 10mA
Output Current sink @5v = 5 - 50mA @15v = 50mA
Output Current source @5v = 100mA @15v = 200mA
Maximum operating frequency 300kHz - 500kHz


Faults with Chip:
Consumes about 10mA when sitting in circuit
Output voltage can be up to 2.5v less than rail voltage
Output can be 0.5v to 1.5v above ground
Sources up to 200mA
Some chips sink only 50mA, some will sink 200mA

A NE555 was tested at 1kHz, 12.75v rail and 39R load.
The Results:
Output voltage 0.5v low, 11.5v high at output current of 180mA
The "test chip" performance was excellent.


HOW TO USE THE 555
        There are many ways to use the 555. They can be used in hundreds of different circuits to do all sorts of clever things. They can also be used as three different types of oscillators:
(a) Astable Multivibrator - constantly oscillates
For frequencies above 1 cycle per second, it is called an oscillator (multivibrator or square wave oscillator).
For frequencies below 1 cycle per second it is called a TIMER or DELAY.
(b) Monostable - changes state only once per trigger pulse - also called a ONE SHOT
(c) Voltage Controlled Oscillator - called a VCO.