Data Sheet
ADA4950-1/ADA4950-2
Rev. A | Page 17 of 28
TERMINOLOGY
+IN
–IN
+OUT
–OUT
+INA
+INB
–INB
–INA
VOCM
RGA
500
VOUT, dm
RL, dm
ADA4950-x
07
95
7-
15
2
RGB
250
RGB
250
RF
500
RF
500
RGA
500
Figure 52. Signal and Circuit Definitions
Differential Voltage
Differential voltage refers to the difference between two node
voltages. For example, the output differential voltage (or equiv-
alently, output differential node voltage) is defined as
VOUT, dm = (V+OUT VOUT)
where V+OUT and VOUT refer to the voltages at the +OUT and
OUT output terminals with respect to a common ground
reference.
The input differential voltage is defined in different ways,
depending upon the selected gain.
For G = 1
VIN, dm = (+INA (INA))
where +INA and INA refer to the voltages at the +INA and
INA input terminals with respect to a common ground
reference (input terminals +INB and INB are floating).
For G = 2
VIN, dm = (+INB (INB))
where +INB and INB refer to the voltages at the +INB and
INB input terminals with respect to a common ground
reference (input terminals +INA and INA are floating).
For G = 3, input terminals +INA and +INB are connected
together, and input terminals INA and INB are connected
together.
VIN, dm = (+INAB (INAB))
where +INAB and INAB refer to the voltages at the connection
of input terminals +INA and +INB and at the connection of
input terminals INA and INB with respect to a common
ground reference.
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
VOUT, cm = (V+OUT + VOUT)/2
Output Balance
Output balance is a measure of how close the output differential
signals are to being equal in amplitude and opposite in phase.
Any imbalances in amplitude or phase produce an undesired
common-mode signal at the amplifier output. Output balance
error is defined as 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
,