OPA4830 Datasheet, PDF (28/45 Pages) National Semiconductor (TI) – Quad, Low-Power, Single-Supply, Wideband Operational Amplifier

OPA4830
SBOS350A – DECEMBER 2006 – REVISED MAY 2008.................................................................................................................................................... www.ti.com
161W
121W
100pF
100pF
1/4
OPA4830
77W
294W
100pF
+5V
100pF
1/4
OPA4830
V_O/V_I = 4V/V
f_-3dB = 10MHz
P_D = 225mW
250W
V_I
500W
250W
250W
500W
V_O
250W
161W
121W
100pF
1/4
OPA4830
100pF
100pF
1/4
OPA4830
77W
294W
100pF
-5V
G_D = 2, w_O = 2p 10MHz, Q = 1.31
G_D = 2, w_O = 2p 10MHz, Q = 0.54
Figure 83. Low-Power, Differential I/O, 4th-Order Butterworth Active Filter
LOW-POWER, DIFFERENTIAL I/O,
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.
While this circuit is bipolar, using ±5V supplies, it can
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.
15
12
9
6
3
0
-3
-6
-9
1
10
100
Frequency (MHz)
Figure 84. Differential 4th-Order, 10MHz
Butterworth Filter
28
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