OPA690 datasheet(28/45 Pages) TI

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1/4

OPA4830

+5V

-5V

1/4

OPA4830

294W

77W

100pF

294W

77W

100pF

250W

1/4

OPA4830

1/4

OPA4830

121W

161W

100pF

500W

100pF

G =2,

p 10MHz,Q=0.54

G =2,

p 10MHz,Q=1.31

121W

161W

100pF

250W

=4V/V

=10MHz

-3dB

P =225mW

500W

100pF

LOW-POWER, DIFFERENTIAL I/O,

Frequency(MHz)

100

-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

bandpass.

The

frequency response for the filter of Figure 83 is

illustrated in Figure 84.

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OPA690 Datasheet(PDF) 28 Page - Texas Instruments

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