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Single-Ended to Fully Differential Application
3-4
Figure 3−3. Output of an AC-Coupled, Single-Supply Application
3
2
1
0
−1
0 500 n 1 Ω
t − Time − s
Volts
The designer should realize that the coupling capacitors, acting with the
gain resistors, produce a high pass characteristic into the circuit.
This application circuit has interaction between R
source
, R
termination
, and R
g
.
Texas Instruments has provided an engineer design utility to facilitate the
design of these circuits. Engineer design utilities are available on the Am-
plifiers and Comparators section of the Analog and Mixed Signal portion of
the TI web page.
Designers should be aware that each individual feedback path is an invert-
ing path. There is no noninverting gain circuit for fully differential amps.
The designer should also be aware that the gain is affected by the open
loop characteristic of the FDA, the same as single−ended op amps. If there
is sufficient safety margin between the closed loop response and open loop
response of the FDA (40 dB or more), the error contribution from the open
loop response of the FDA is negligible and can be ignored.