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AD830 Datasheet PDF : 16 Pages
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AD830
INTERFACING THE INPUT
Common-Mode Voltage Range
The common-mode range of the AD830 is defined by the am-
plitude of the differential input signal and the supply voltage.
The general definition of common-mode voltage, VCM, is usu-
ally applied to a symmetrical differential signal centered about a
particular voltage as illustrated by the diagram in Figure 23.
This is the meaning implied here for common-mode voltage.
The internal circuitry establishes the maximum allowable volt-
age on the input or feedback pins for a given supply voltage.
This constraint and the differential input voltage sets the
common-mode voltage limit. Figure 24 shows a curve of the
common-mode voltage range vs. differential voltage for three
supply voltage settings.
VMAX
VPEAK
VCM
Differential Voltage Range
The maximum applied differential voltage is limited by the clip-
ping range of the input stages. This is nominally set at 2.4 volts
magnitude and depicted in the crossplot (X-Y) photo of Figure
25. The useful linear range of the input stages is set at 2 volts,
but is actually a function of the distortion required for a particu-
lar application. The distortion increases for larger differential
input voltages. A plot of relative distortion versus input differen-
tial voltage is shown in Figures 8 and 11 in the Typical Charac-
teristics section. The distortion characteristics could impose a
secondary limit to the differential input voltage for high accu-
racy applications.
1V
1V
100
90
Figure 23. Common-Mode Definition
15
+VCM
±15V = VS
12
–VCM
+VCM
9
±10V = VS
6
–VCM
+VCM
3
±5V = VS
–VCM
0
0
0.4
0.8
1.2
1.6
2.0
DIFFERENTIAL INPUT VOLTAGE – VPEAK
Figure 24. Input Common-Mode Voltage Range vs.
Differential Input Voltage
10
0%
Figure 25. Clipping Behavior
15
VP
12
9
VN
6
3
0
0
4
8
12
16
20
SUPPLY VOLTAGE – Volts
Figure 26. Maximum Output Swing vs. Supply
–10–
REV. A
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