The document discusses the operation and implementation of multivibrators, specifically bistable, astable, and monostable configurations. It elaborates on using the IC 555 timer to create these circuits, explaining triggers, output states, and the behavior of the circuits during charging and discharging processes. Key concepts include feedback loops and the significance of resistor values in the 555 timer's functionality.

1. UNIT-5
Mohammad Asif Iqbal
Assistant Professor,
Deptt of ECE,
JETGI, Barabanki

2. MULTIVIBRATORS
BISTABLE
ASTABLE
MONOSTABLE

3. BISTABLE

5. Now consider what will happen as Vi is decreased from L-

6. Astable Multivibrator(No stable state)
A square waveform can be generated by arranging for a bistable
multivibrator to switch states periodically.
This can be done by connecting the bistable multivibrator with an
RC circuit in a feedback loop.

7. Performance and operation..
charging
v+=v-
discharg
ing

8. Monostable Multivibraotor(one stable state)
Vp >Vn, Vo = L+
Vp <Vn, Vo = L-

9. L+
Forward bias
Vn
=0
L-Reverse bias
=-ve & will
vary
exponentially

10. Monostable Multivibrator
L+
=0
Vp > Vn, Vo = L+
Vp <Vn, Vo = L-
Forward bias for only
–ve triggering pulse
Diode will conduct
heavily and pull Vp
down
L-
=-ve
Vp -Vn= +ve
L+

11. IC 555 Timer
Remember!
Its your SR
Op-amp
And output
will be
regarded as
1 for L+ & 0
for L-
Q: why it is
known as IC
555
A: Because
of these
resisters.
They are of
5k ohm.
S R Q Q’
0 0 No change
0 1 Reset
1 0 Set

12. Implementing a monostable Multivibrator using 555 IC
0
1
ON
Vp <Vn, Vo = L-
0We
keep
Vtrigger
>VTL
0
Lets
trigger
1
Vp >Vn, Vo = L+
1
0
OFF
Q:How long it
will remain 1?
Just for that
much span
of time, after
that
triggering
pulse will
become
positive and
o/p of
comparator
2 goes to 0.
Vp >Vn, Vo = L+
1
0
1
0
0
Q:Justify the
difference
between
charging and
discharging
time
Q:Justify the
difference
between
charging and
discharging
time
A: Look the
difference
between the
time
constant.

13. Implementing a Astable Multivibrator using 555 IC
0
1
OFF
Vp >
Vn >
0
1
0
1
ON
Vn >
0
Vp >
1
1
0

14. THANK YOU!