OPA2683 Datasheet, PDF (18/33 Pages) Texas Instruments – Very Low-Power, Dual, Current-Feedback Operational Amplifier

DESIGN-IN TOOLS
DEMONSTRATION FIXTURES
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.
PRODUCT
OPA2683ID
OPA2683IDCN
OPA2683IDGS
PACKAGE
SO-8
SOT23-8
MSOP-10
ORDERING
NUMBER
LITERATURE
NUMBER
DEM-OPA-SO-2A
DEM-OPA-SOT-2A
DEM-OPA-MSOP-2B
SBOU003
SBOU001
SBOU040
TABLE I. Demonstration Fixtures by Package.
The demonstration fixtures can be requested at the Texas
Instruments web site (www.ti.com) through the OPA2683
product folder.
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.
OPERATING SUGGESTIONS
SETTING RESISTOR VALUES TO OPTIMIZE BANDWIDTH
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.
V_I
i_ERR
α
R_I
R_G
V_O
Z_(S) i_ERR
R_F
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
R_I ⇒ Buffer output impedance
i_ERR ⇒ Feedback error current signal
Z(s) ⇒ Frequency dependent open-loop transimpedance
gain from i_ERR to V_O
18
OPA2683
www.ti.com
SBOS244H