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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.
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