Datasheet

OPA3692
SBOS228E
13
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 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
402Ω
402Ω
120pF
82pF
220pF
22pF
68pF
47.5Ω
124Ω
1/3
OPA3692
402Ω
56pF
110Ω
255Ω
402Ω
1/3
OPA3692
402Ω
402Ω
180pF
48.7Ω
95.3Ω
49.9Ω
(open)
(open)
V
OUT
V
IN
20
–0
–20
–40
–60
–80
–100
Frequency (MHz)
1 10003 10 30 100 300
7TH-ORDER BUTTERWORTH
FILTER RESPONSE
Gain (dB)