Datasheet

1/4
OPA4830
+5V
-5V
1/4
OPA4830
294W77W
100pF
294W77W
100pF
250W
250W
V
O
V
I
1/4
OPA4830
1/4
OPA4830
121W161W
100pF
500W
100pF
G =2, =2w p 10MHz,Q=0.54
D O
G =2, =2w p 10MHz,Q=1.31
D O
121W161W
100pF
250W
250W
V =4V/V/V
O I
f =10MHz
-3dB
P =225mW
D
500W
100pF
100pF
100pF
LOW-POWER, DIFFERENTIAL I/O,
Frequency(MHz)
DifferentialGain(dB)
1 10 100
15
12
9
6
3
0
-3
-6
-9
OPA4830
SBOS350A – DECEMBER 2006 – REVISED MAY 2008 .................................................................................................................................................... www.ti.com
Figure 83. Low-Power, Differential I/O, 4th-Order Butterworth Active Filter
4th-ORDER ACTIVE FILTER
The OPA4830 can give a very capable gain block for
active filters. The quad design lends itself very well to
differential active filters. Where the filter topology is
looking for a simple gain function to implement the
filter, the noninverting configuration is preferred to
isolate the filter elements from the gain elements in
the design. See Figure 83 for an example of a
10MHz, 4th-order Butterworth, low-pass Sallen-Key
filter. The design places the higher Q stage first to
allow the lower Q 2nd stage to roll off the peaked
noise of the first stage. The resistor values have been
adjusted slightly to account for the amplifier group
delay.
Figure 84. Differential 4th-Order, 10MHz
While this circuit is bipolar, using ± 5V supplies, it can
Butterworth Filter
easily be adapted to single-supply operation. This
configuration adds two real zeroes in the response,
transforming this circuit into a bandpass. The
frequency response for the filter of Figure 83 is
illustrated in Figure 84 .
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