lecture 12

7.2.4 Monostable and astable multivibrator:
As we said above, a monostable multivibrator has only one stable state, the
other state being momentary. An astable multivibrator has no stable state; it oscillates
back and forth between two states. The integrated circuit NE555 is a multivibrator
which cans both function as monostable and as astable.
7.2.4.1 IC NE555:
The 555 integrated circuit is the most popular ship ever manufactured.
Independently manufactured by more than 10 manufacturers, still in current
production, and almost 40 years old, this little circuit has withstood the test of time. It
has been used in many things from toys to spacecraft. The IC 555 integrates a flip- flop
circuit, and also operational amplifiers. The basic internal constitution of the IC 555 is
given as follows

7.2.4.2 IC 555 as monostable:
A mechanical analogy of a monostable multivibrator would be a momentary
contact push button switch which returns to its normal (stable) position when pressure
is removed from its button actuator. In order to work as monostable multivibrator, the
IC 555 should be connected as follows. The circuit is designed here using the
electronic simulation software ISIS Professional edited by Labcenter. Values of
component appearing on the diagram are just suggested.