Datasheet

AD8138
Rev. F | Page 16 of 24
OPERATIONAL DESCRIPTION
DEFINITION OF TERMS
AD8138
+IN
–IN
+OUT
–OUT
C
F
C
F
R
F
R
F
+D
IN
–D
IN
V
OCM
R
G
R
G
V
OUT, dm
R
L, dm
01073-041
Figure 42. Circuit Definitions
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 reference.
Common-mode voltage refers to the average of two node
voltages. The output common-mode voltage is defined as
V
OUT, cm
= (V
+OUT
+ V
−OUT
)/2
Balance is a measure of how well differential signals are
matched in amplitude and exactly 180° apart in phase. 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’s midpoint with the
magnitude of the differential signal (see
Figure 41). By this
definition, output balance is the magnitude of the output
common-mode voltage divided by the magnitude of the output
differential mode voltage:
dmOUT
cmOUT
V
V
ErrorBalanceOutput
,
,
=