ada4950-1 Analog Devices, Inc., ada4950-1 Datasheet - Page 18

• Manufacturer Part Number: ada4950-1
• Description: Low Power, Selectable Gain Differential Adc Driver, G = 1, 2, 3
• Manufacturer: Analog Devices, Inc.

ADA4950-1/ADA4950-2
THEORY OF OPERATION
The ADA4950-x differs from conventional op amps in that it has
two outputs whose voltages move in opposite directions and an
additional input, V
gain and negative feedback to force these outputs to the desired
voltages. The ADA4950-x behaves much like a standard voltage
feedback op amp and facilitates single-ended-to-differential
conversions, common-mode level shifting, and amplifications
of differential signals. Like an op amp, the ADA4950-x has high
input impedance at its internal input terminals (to the right of
the internal gain resistors) and low output impedance. Because
it uses voltage feedback, the ADA4950-x manifests a nominally
constant gain bandwidth product.
OCM
. Like an op amp, it relies on high open-loop
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Two feedback loops are used to control the differential and
common-mode output voltages. The differential feedback loop,
set with on-chip feedback and gain resistors, controls only the
differential output voltage. The common-mode feedback loop is
internal to the actual amplifier and controls only the common-
mode output voltage. This architecture makes it easy to set the
output common-mode level to any arbitrary value within the
specified limits. The output common-mode voltage is forced, by
the internal common-mode feedback loop, to be equal to the
voltage applied to the V
The internal common-mode feedback loop produces outputs
that are highly balanced over a wide frequency range without
requiring tightly matched external components. This results in
differential outputs that are very close to the ideal of being
identical in amplitude and that are exactly 180° apart in phase.
OCM
input.