B&B Electronics 4 Channel Input Buffer Board SDAIBB User Manual
Page 16
14 SDAIBB1300
Manual
B&B Electronics Mfg Co Inc – 707 Dayton Rd - PO Box 1040 - Ottawa IL 61350 - Ph 815-433-5100 - Fax 815-433-5104
Maximum Differential
To determine the maximum differential voltage that can be
amplified, the gain and the common mode voltage must be known first.
Using this information, the most positive the differential voltage may be is
calculated using Equation 12. Equation 13 is used to calculate the most
negative that the differential voltage may swing. These two values are still
limited by the maximum allowable swing given by Equation 14.
Example: Find the allowable swing of a signal with a common mode
voltage of 1V with a gain of 50.
From Equation 12:
(
)
136
.
0
50
1
4
.
4
2
=
−
=
DIFF
V
From Equation 13:
(
)
0636
.
0
50
590
.
0
1
2
+
=
DIFF
V
From Equation 14:
0988
.
0
50
94
.
4
=
≤
InputRange
The differential voltage can swing as negative as –0.0636 V and as positive
as 0.136 V. However, this full range cannot be achieved with the same
output offset setting due to the 0.0988 V range from Equation 14. To find
the output offset voltage that allows the lower end of this range, use
Equation 1 with Vout set to 0.01 V.
(
)
et
OutputOffs
G
IN
IN
V
out
+
−
=
−
+
Rearranged to calculate the desired output offset it looks like this
G
V
V
et
OutputOffs
DIFF
out
×
−
=
Substitute in the appropriate values and solve for the output offset.
(
)
V
et
OutputOffs
19
.
3
50
0636
.
0
01
.
0
=
×
−
−
=
Equation 12:
(
)
G
V
V
CM
DIFF
−
=
4
.
4
2
Equation 13:
(
)
G
V
V
V
CM
DIFF
590
.
0
2
+
=
Equation 14:
G
V
InputRange
94
.
4
≤