Multivibrators
(sometimes called FLIP-FLOPS) have two "cross coupled" transistors, say
TR1 and TR2.
This causes
TR1 to be on (conducting) and TR2 off.
They can be
made to reverse states, with TR1 turning off and TR2 turning on.
The states of
the transistors can be indicated using a lamp for each transistor.
THE ASTABLE
is continually changing state.
The lights flash
alternately on and off.
This is because
it has two UNSTABLE states and is changing automatically from one to the
other.
The duration
of these states is determined by two RESISTOR/CAPACITOR TIME CONSTANTS.
Changing the
values of the time constants alters the flashing rate.
THE MONOSTABLE
has one unstable and one stable state.
It rests in
the stable state, waiting for an external pulse.
When a pulse
arrives it changes to the unstable state.
It stays in
the unstable state for a time determined by an RC time constant.
It then falls
back into the stable state and waits for another pulse.
This means that
the lights wait in the stable state, one on, the other off.
When the pulse
arrives they change state for a while and then fall back to the waiting
state.
THE BISTABLE
has two stable states.
It waits in
one state for an external pulse.
When the pulse
arrives it changes into the other stable state waiting for another pulse.
If another pulse
never arrives it will wait forever.
The lights change
over on the arrival of each pulse. |
