Hardware Reference
In-Depth Information
V 0
V 01
V 02
¼
V 02
I x 2 ¼
ð
15
:
27
Þ
R 1
R 1
V 0
R 2
V 01
R 2 ¼
I z 2 ¼
ð
15
:
28
Þ
and setting I x2 ¼
I z2 , which leads to the following values of V TL and V TH
V 0
R 1
R 2
V TH ¼
V TL ¼
1
ð
15
:
29
Þ
The amplitude (peak-to-peak) of the triangular wave form is given by:
V 0
R 1
R 2
V 02 ¼
ð
V TH
V TL
Þ ¼
21
ð
15
:
30
Þ
The periods of the square and triangular waves are given by:
2 R 3 C 1
ð
ð
R 1 =
R 2
Þ
Þ
T 1 ¼
ð
15
:
31
Þ
V c
2 R 3 C 1
ð
ð
R 1 =
R 2
Þ
Þ
T 2 ¼
ð
15
:
32
Þ
2
V c
Finally, the oscillation frequency (f 0 ) and duty cycle (D a ) are given by:
1
T 1 þ
V C 2
ð
V C
Þ
f 0 ¼
T 2 ¼
ð
15
:
33
Þ
4 R 3 C 1
ð
ð
R 1 =
R 2
Þ
Þ
T 1
T 1 þ
V C
2
D a ¼
T 2 ¼
ð
:
Þ
1
15
34
where
V B
V 0
V C ¼
1
ð 15 : 35 Þ
It is interesting to note that f 0 can be independently controlled by R 3 thereby
resulting in single resistance controlled oscillator. Also, the amplitude of the
triangular wave is proportional to the ratio (R 1 /R 2 ) whereas the duty cycle is
controllable by the control voltage V c . Furthermore, if one takes V c <<
1 the
interval T 2 is negligibly small and can be ignored and the circuit can then be used
as saw-tooth waveform generator for which the frequency of oscillation is given by:
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