Datasheet

DIFFERENTIAL RECEIVER/DRIVER SINGLE-SUPPLY MFB DIFFERENTIAL
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
V =1+
DIFF
V (- -V )
I I
2R
F
R
G
1/2
OPA2889
1/2
OPA2889
Gain(dB)
Frequency(Hz)
10k
100k
1M
10M
3
0
-
-
-
-
3
6
9
12
OPA2889
SBOS373B – JUNE 2007 – REVISED AUGUST 2008 ....................................................................................................................................................... www.ti.com
ACTIVE FILTER: 2MHz BUTTERWORTH
A very versatile application for a dual operational
CONFIGURATION
amplifier is the differential amplifier configuration
shown in Figure 57 . With both amplifiers of the The active filter circuit illustrated in Figure 59 can be
OPA2889 connected for noninverting operation, the easily implemented using the OPA2889. In this
circuit provides a high input impedance whereas the configuration, each amplifier of the OPA2889
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,
whereas the ac gain still follows the standard transfer
function of G = 1 + 2R
F
/R
G
. This 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 58 . 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 57. High-Speed Differential Receiver
Figure 58. Multiple Feedback Filter Frequency
Response
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