B&B Electronics 4 Channel Input Buffer Board SDAIBB User Manual
Page 15
SDAIBB1300 Manual
13
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
Maximum and Minimum Common Mode Voltage
If the differential voltage range and desired gain are known, the
maximum and minimum common mode voltage can be determined.
Equation 10 is used to calculate the maximum common mode voltage
knowing the gain and the differential voltage. Equation 11 is used to
calculate the minimum common mode voltage. Remember that when
Input+ or Input- is connected to GND on the SDAIBB the
common mode voltage changes as the differential voltage changes.
Equation 10:
2
4
.
4
G
V
V
V
DIFF
CMMAX
×
−
=
Equation 11:
2
590
.
0
G
V
V
V
DIFF
CMMIN
×
+
−
=
Example: Find the allowable range of the common mode voltage for a
input range of ±100 mV with a gain of 10.
From Equation 10:
V
V
CMMAX
9
.
3
2
10
1
.
0
4
.
4
=
×
−
=
From Equation 11:
V
V
CMMIN
09
.
0
2
10
1
.
0
590
.
0
−
=
×
+
−
=
The common mode voltage must be between –0.09 and 3.9 V.