Datasheet

OPA3691
SBOS227E
16
www.ti.com
ORDERING LITERATURE
PRODUCT PACKAGE NUMBER NUMBER
OPA3691IDBQ SSOP-16 DEM-OPA-SSOP-3A SBOU006
OPA3691ID SO-16 DEM-OPA-SO-3A SBOU007
DESIGN-IN TOOLS
DEMONSTRATION FIXTURES
Two printed circuit boards (PCBs) are available to assist in
the initial evaluation of circuit performance using the OPA3691
in its two package options. Both of these are offered free of
charge as unpopulated PCBs, delivered with a user's guide.
The summary information for these fixtures is shown in the
table below.
FIGURE 8. Wideband Programmable Gain.
1/3
OPA3691
73.2Ω
20Ω
191Ω 365Ω
1/3
OPA3691
68.1Ω
20Ω
61.2Ω 274Ω
1/3
OPA3691
63.4Ω
20Ω
20Ω 182Ω
74HC238
50Ω Load
–5V
+5V
Power-supply
decoupling not shown.
V
IN
+5V
D
1
D
2
Y
0
Y
1
Y
2
50Ω
active devices, like the OPA3691, where parasitic capaci-
tance and inductance can have a major effect on frequency
response.
SPICE models will be available through the TI web page or
on a disk (call our Applications Department). 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 differential gain and phase characteristics. These models
do not distinguish between the AC performance of different
package types.
OPERATING SUGGESTIONS
SETTING RESISTOR VALUES TO
OPTIMIZE BANDWIDTH
A current-feedback op amp like the OPA3691 can hold an
almost constant bandwidth over signal gain settings with the
proper adjustment of the external resistor values. This is
shown in the Typical Characteristics; the small-signal band-
width decreases only slightly with increasing gain. These
curves also show that the feedback resistor has been changed
for each gain setting. The resistor
values on the inverting side
The demonstration fixtures can be requested at the Texas
Instruments web site (www.ti.com) through the OPA3691
product folder.
SPICE MODELS
Computer simulation of circuit performance using SPICE is
often useful when analyzing the performance of analog
circuits and systems. This is particularly true for high-speed