ADA4939-1/ADA4939-2
Rev. 0 | Page 16 of 24
OPERATIONAL DESCRIPTION
DEFINITION OF TERMS
+IN
–IN
+OUT
–OUT
+DIN
–FB
+FB
–DIN
VOCM
RG
RF
RG
VOUT, dm
RL, dm
RF
ADA4939
074
29
-04
9
Figure 42. 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
VOUT, dm = (V+OUT VOUT)
where V+OUT and VOUT refer to the voltages at the +OUT and
OUT terminals with respect to a common reference.
Common-Mode Voltage
Common-mode voltage refers to the average of two node
voltages. The output common-mode voltage is defined as
VOUT, cm = (V+OUT + VOUT)/2
Balance
Output balance is a measure of how close the 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 (see
Figure 39). 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
Error
Balance
Output
,
=