AD830
INTERFACING TH E INP UT
D iffer ential Voltage Range
Com m on-Mode Voltage Range
T he maximum applied differential voltage is limited by the clip-
ping range of the input stages. T his is nominally set at 2.4 volts
magnitude and depicted in the crossplot (X-Y) photo of Figure
25. T he 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. T he 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 T ypical Charac-
teristics section. T he distortion characteristics could impose a
secondary limit to the differential input voltage for high accu-
racy applications.
T he common-mode range of the AD830 is defined by the am-
plitude of the differential input signal and the supply voltage.
T he 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.
T his is the meaning implied here for common-mode voltage.
T he internal circuitry establishes the maximum allowable volt-
age on the input or feedback pins for a given supply voltage.
T his 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.
1V
1V
V
MAX
100
90
V
CM
V
PEAK
Figure 23. Com m on-Mode Definition
10
0%
15
+VCM
±15V = VS
12
–VCM
Figure 25. Clipping Behavior
+VCM
9
15
±10V = VS
V
P
6
–VCM
12
9
+VCM
±5V = VS
3
V
N
–VCM
0
6
3
0
0.4
0.8
1.2
1.6
2.0
DIFFERENTIAL INPUT VOLTAGE – VPEAK
Figure 24. Input Com m on-Mode Voltage Range vs.
Differential Input Voltage
0
0
4
8
12
16
20
SUPPLY VOLTAGE – Volts
Figure 26. Maxim um Output Swing vs. Supply
–10–
REV. A
ADI [ ADI ]
