Datasheet

1/3
OPA3832
+5V
-5V
V
O
50W
V
IN
400W
175W
50 SourceW
150W
400W
6.8 Fm
+
6.8 Fm
+
0.1 Fm
0.1 Fm
0.01 Fm
SINGLE-SUPPLY ACTIVE FILTER
9
6
3
0
-3
-6
-9
-12
-15
-18
Frequency(Hz)
100 1k 10k 100k 1M 10M
Gain(dB)
1/3
OPA3832
400W
2kW
400W
+5V
3kW
2V
I
V
I
300pF
0.1 Fm
1MHz,2nd-Order
ButterworthFilter
470pF
866W205W
0.1 Fm
OPA3832
www.ti.com ............................................................................................................................................ SBOS370A – DECEMBER 2006 – REVISED AUGUST 2008
pole set to 3.2kHz for the component values shown).
As discussed for Figure 46 , this configuration allows
the midpoint bias formed by one 2k Ω and one 3k Ω
resistor to appear at both the input and output pins.
The midband signal gain is set to +2 (6dB) in this
case. The capacitor to ground on the noninverting
input is intentionally set larger to dominate input
parasitic terms. At a gain of +2, the OPA3832 on a
single supply will show 80MHz small- and large-signal
bandwidth. The resistor values have been slightly
adjusted to account for this limited bandwidth in the
amplifier stage. Tests of this circuit, shown in
Figure 49 , illustrate a precise 1MHz, – 3dB point with
a maximally-flat passband (above the 3.2kHz
ac-coupling corner), and a maximum stop band
attenuation of 36dB.
Figure 48. DC-Coupled, G = +2, Bipolar Supply
Specification and Test Circuit
The OPA3832, while operating on a single +3.3V or
+5V supply, lends itself well to high-frequency active
filter designs. Again, the key additional requirement is
to establish the dc operating point of the signal near
the supply midpoint for highest dynamic range.
Figure 50 shows an example design of a 1MHz
low-pass Butterworth filter using the Sallen-Key
topology.
Figure 49. 1MHz, 2nd-Order, Butterworth
Both the input signal and the gain setting resistor are
Low-Pass Filter
ac-coupled using 0.1 µ F blocking capacitors (actually
giving bandpass response with the low-frequency
Figure 50. Single-Supply, High-Frequency Active Filter
Copyright © 2006 – 2008, Texas Instruments Incorporated Submit Documentation Feedback 19
Product Folder Link(s): OPA3832