DESIGN-IN TOOLS
OPERATING SUGGESTIONS
DEMONSTRATION FIXTURES
SETTING RESISTOR VALUES TO OPTIMIZE BANDWIDTH
Two printed circuit boards (PCBs) are available to assist in
the initial evaluation of circuit performance using the OPA2683
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
Table I.
Any current-feedback op amp like the OPA2683 can hold
high bandwidth over signal-gain settings with the proper
adjustment of the external resistor values. A low-power part
like the OPA2683 typically shows a larger change in band-
width due to the significant contribution of the inverting input
impedance to loop-gain changes as the signal gain is changed.
Figure 13 shows a simplified analysis circuit for any current-
feedback amplifier.
ORDERING
NUMBER
LITERATURE
NUMBER
PRODUCT
PACKAGE
OPA2683ID
OPA2683IDCN
OPA2683IDGS
SO-8
SOT23-8
MSOP-10
DEM-OPA-SO-2A
DEM-OPA-SOT-2A
DEM-OPA-MSOP-2B
SBOU003
SBOU001
SBOU040
VI
TABLE I. Demonstration Fixtures by Package.
α
VO
The demonstration fixtures can be requested at the Texas
Instruments web site (www.ti.com) through the OPA2683
product folder.
RI
Z(S) iERR
iERR
RF
MACROMODELS
Computer simulation of circuit performance using SPICE is
often useful when analyzing the performance of analog
circuits and systems. This is particularly true for higher speed
designs where parasitic capacitance and inductance can
have a major effect on circuit performance. A SPICE model
for the OPA683 is available in the product folder on the TI
web site (www.ti.com). This is the single channel model for
the OPA2683—simply use two of these to implement an
OPA2683 simulation. These models do a good job of predict-
ing small-signal AC and transient performance under a wide
variety of operating conditions. However, they are less accu-
rate in predicting the harmonic distortion or dG/dP character-
istics. These models do not attempt to distinguish between
the package types in their small-signal AC performance.
RG
FIGURE 13. Current-Feedback Transfer Function Analysis
Circuit.
The key elements of this current-feedback op amp model are:
α
Buffer gain from the noninverting input to the inverting input
Buffer output impedance
RI
iERR
Feedback error current signal
Z(s)
Frequency dependent open-loop transimpedance
gain from iERR to VO
OPA2683
SBOS244H
18
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TI [ TEXAS INSTRUMENTS ]
