Datasheet

AD8475 Data Sheet
Rev. C | Page 16 of 24
TERMINOLOGY
+IN
VOCM
–IN
+OUT
–OUT
V
OUT, dm
R
L, dm
AD8475
1kΩ
1.25kΩ
1.25kΩ
1kΩ
09432-162
Figure 48. Signal and Circuit Definitions
Differential Voltage
Differential voltage refers to the difference between two
node voltages. For example, the output differential voltage (or
equivalently, output differential mode voltage) is defined as
V
OUT, dm
= (V
+OUT
− V
−OUT
)
where V
+OUT
and V
−OUT
refer to the voltages at the +OUT and
−OUT terminals with respect to a common ground reference.
Similarly, the differential input voltage is defined as
V
IN, dm
= (V
+IN
− (V
−IN
))
Common-Mode Voltage
Common-mode voltage refers to the average of two node voltages
with respect to the local ground reference. The output common-
mode voltage is defined as
V
OUT, cm
= (V
+OUT
+ V
−OUT
)/2
The input common-mode voltage is defined as
V
IN, cm
= (V
+IN
+ V
−IN
)/2
Balance
Output balance is a measure of how close the output differential
signals are to being equal in amplitude and opposite in phase.
Output balance is most easily determined by placing a well-
matched resistor divider between the differential voltage nodes
and comparing the magnitude of the signal at the divider midpoint
with the magnitude of the differential signal. By this definition,
output balance is the magnitude of the output common-mode
voltage divided by the magnitude of the output differential
mode voltage.
dm
OUT
cm
OUT
V
V
Error
Balance
Output
,
,
∆
∆
=