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a
b
I
z
I
z
z
V
0
z
V
0
R
2
DVCC
y
2
R
2
DVCC
y
2
V
trg
y
1
x
V
trg
y
1
x
I
x
I
x
R
1
R
1
C
M
+
−
V
c
D
C
c
V
trg
(t)
V
0
(t)
t
0
V
0+
0
t
T
V
0−
quasi-stable state
stable state
V
c
(t)
0
V
TL
t
T
r
recovery time state
T
1
T
2
T
3
Fig. 15.11 DVCC based monostable multivibrators (a) the basic circuit (b) the modified circuit
shortened recovery time (c) corresponding waveforms (Adapted from [
14
]
2011 Elsevier Ltd.)
©
V
0
R
1
R
2
V
TL
¼
V
c
TðÞ
¼
1
ð
15
:
46
Þ
By substituting the value of V
c
(T
2
) in the general expression for the capacitor
voltage time period T which is found to be:
V
TL
V
0
R
2
R
1
T
¼
T
2
T
1
¼
R
1
Cin
1
¼
R
1
Cin
ð
15
:
47
Þ
By a routine analysis, the recovery times T
r
for both the circuits are defined as
T
r
¼
(T
3
-T
2
) and are found to be:
if R
DR
>>
R
1
R
2
T
r
¼
T
3
T
2
R
1
C
ln 2
R
1
ð
15
:
48
Þ
where R
DR
is the turn-off resistance of the diode D.
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