Hardware Reference
In-Depth Information
a
b
I
z1
I
z2
V
01
V
02
z
+
V
01
z
+
V
0+
V
TH
DO-DVCC
y
2
y
1
V
02
x
t
0
R
2
C
I
x
R
1
V
TL
V
0−
T
1
T
2
Fig. 15.13 DO-DVCC based square/triangular waveform generator employing grounded passive
components [
16
](a) proposed circuit (b) its relevant waveforms
for the capacitor voltage following a negative ramp and the currents I
x
and I
z
in this
state are given by the following equations:
V
0
dV
02
t
ðÞ
R
2
C
¼
V
01
V
TL
V
TH
¼
R
2
C
¼
ð
15
:
58
Þ
dt
T
2
V
0
V
01
V
02
¼
V
02
I
X
¼
ð
:
Þ
15
59
R
1
R
1
V
0
R
2
V
01
R
2
¼
I
z
¼
I
z
1
¼
I
z
2
¼
ð
15
:
60
Þ
Using the above equations and setting Ix¼ I
Z
, the expressions for the threshold
voltages are found to be:
V
0
R
1
R
2
V
TH
¼
V
TL
¼
1
ð
15
:
61
Þ
The oscillation frequency of the waveforms generated by this circuit is found to be:
1
T
1
þ
1
f
0
¼
T
2
¼
ð
15
:
62
Þ
4
R
2
C
1
ð
ð
R
1
=
R
2
Þ
Þ
From the experiments based upon realizing DVCC using commercially available
AD844AN ICs, it has been found that in the discrete bread boarded versions of the
circuit, the maximum attainable oscillation frequency of the circuit has been found
to be several hundred KHz (500-800 KHz) which is still larger than those attainable
from square/triangular waveform generators using op-amps or OTAs (which were
found to be well below 100 KHz). In view of the simplicity of the structure coupled
with its good performance, it appears that the circuit may find applications in
instrumentation, communication and signal processing systems.
Search WWH ::
Custom Search