Datasheet

1
2 R Cp ´´ ´
f =
O
R =R =0.65 R
1 2
´
´
´
R =0.375 R
C =C
C =2 C
3
1
2
50W
V
I
-V
I
R
O
R
O
R
F
750W
R
F
750W
50W
R
G
1/2
OPA2890
1/2
OPA2890
V =1+
DIFF
V (- -V )
I I
2R
F
R
G
Gain(dB)
Frequency(Hz)
10k 100k 1M
10M
3
0
-3
-6
-12
-9
OPA2890
SBOS364C –DECEMBER 2007–REVISED DECEMBER 2009 www.ti.com
DIFFERENTIAL RECEIVER/DRIVER SINGLE-SUPPLY MFB DIFFERENTIAL
ACTIVE FILTER: 2MHz BUTTERWORTH
A very versatile application for a dual operational
CONFIGURATION
amplifier is the differential amplifier configuration
shown in Figure 56. With both amplifiers of the The active filter circuit illustrated in Figure 58 can be
OPA2890 connected for noninverting operation, the easily implemented using the OPA2890. In this
circuit provides a high input impedance, while the configuration, each amplifier of the OPA2890
gain can easily be set by just one resistor, R
G
. When operates as an integrator. For this reason, this type of
operated in low gains, the output swing may be application is also called an infinite gain filter
limited as a result of the common-mode input swing implementation. A Butterworth filter can be
limits of the amplifier itself. An interesting modification implemented using the following component ratios:
of this circuit is to place a capacitor in series with R
G
.
Now the dc gain for each side is reduced to +1V/V;
the ac gain follows the standard transfer function of G
= 1 + 2R
F
/R
G
. This configuration might be
advantageous for applications processing only a
frequency band that excludes dc or very low
frequencies. An input dc voltage resulting from input
bias currents is not amplified by the ac gain and can
be kept low. This circuit can be used as a differential
The frequency response for a 2MHz Butterworth filter
line receiver, driver, or as an interface to a differential
is shown in Figure 57. One advantage for using this
input ADC.
type of filter is the independent setting of ω
o
and Q. Q
can be easily adjusted by changing the R
3A, B
resistors without affecting ω
o
.
Figure 56. High-Speed Differential Receiver
Figure 57. Multiple Feedback Filter Frequency
Response
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