OPA690 datasheet(13/27 Pages) TI

13 / 27 page

OPA3692

SBOS228E

www.ti.com

LOW-PASS FILTER

The circuit in Figure 6 realizes a 7th-order Butterworth low-

pass filter with a –3dB bandwidth of 20MHz. This filter is based

on the KRC active filter topology, which uses an amplifier with

the fixed gain

≥ 1. The OPA3692 makes a good amplifier for

this type of filter. The component values have been adjusted

to compensate for the parasitic effects of the op amp.

DESIGN-IN TOOLS

DEMONSTRATION FIXTURES

Two PCBs are available to assist in the initial evaluation of

circuit performance using the OPA3692 in its two package

options. Both of these are offered free of charge as

unpopulated PCBs, delivered with a user's guide. The sum-

mary information for these fixtures is shown in

Table I.

The demonstration fixtures can be requested at the Texas

Instruments web site at (www.ti.com) through the OPA3692

product folder.

MACROMODELS AND APPLICATIONS SUPPORT

Computer simulation of circuit performance using SPICE is

often useful when analyzing the performance of analog

circuits and systems. This is particularly true for video and RF

amplifier circuits where parasitic capacitance and inductance

can have a major effect on circuit performance. A SPICE

model for the OPA692 is available through the Texas Instru-

ments web site at www.ti.com. Use three of these models to

simulate the OPA3692. These models do a good job of

predicting small-signal AC and transient performance under

a wide variety of operating conditions. They do not do as well

in predicting the harmonic distortion or dG/dP characteristics.

These models do not attempt to distinguish between the

package types in their small-signal AC performance.

FIGURE 6. 7th-Order Butterworth Filter.

ORDERING

LITERATURE

PRODUCT

PACKAGE

NUMBER

OPA3692IDBQ

SSOP-16

DEM-OPA-SSOP-3B

SBOU006

OPA3692ID

SO-16

DEM-OPA-SO-3A

SBOU007

TABLE I. OPA3692 Demonstration Boards.

1/3

OPA3692

402

Ω

402

Ω

120pF

82pF

220pF

22pF

68pF

47.5

Ω

124

Ω

1/3

OPA3692

402

Ω

56pF

110

Ω

255

Ω

402

Ω

1/3

OPA3692

402

Ω

402

Ω

180pF

48.7

Ω

95.3

Ω

49.9

Ω

(open)

OUT

–0

–20

–40

–60

–80

–100

Frequency (MHz)

1000

100

300

7TH-ORDER BUTTERWORTH

FILTER RESPONSE

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