OPA3680 Burr-Brown, OPA3680 Datasheet - Page 14

• Manufacturer Part Number: OPA3680
• Description: Triple / Wideband / Voltage-Feedback OPERATIONAL AMPLIFIER With Disable
• Manufacturer: Burr-Brown

FIGURE 8. State Variable Filter.
STATE VARIABLE FILTER
Figure 8 shows a state variable filter using the OPA3680.
This active filter is quite useful for high Q filter responses,
and will produce lowpass, highpass, bandpass, notch and
allpass functions. The filter response is:
The desired filter frequency response is achieved by the
correct selection of the feed-forward components at the
input.
The resistor R
driver from capacitive loading problems when
ensure good performance, make sure that:
where, f
(300MHz).
V
GBP
V
OUT
P
IN
®
is the OPA3680’s gain bandwidth product
V
RC
ISO
1
IN
OPA3680
–
2
isolates the last op amp and the input
P
s
2
20
f
f
GBP
20
GBP
s
Q
2
s
49.9
Q
Q
Q
P
R/
,
P
P
P
R/
R/
P
C
,
s
Q
Q
Q
P
P
–
P
P
OPA3680
1
1
2
P
1/3
R
ISO
C
2
P
> 0. To
49.9
R
(2)
(3)
14
OPA3680
DESIGN-IN TOOLS
DEMONSTRATION BOARDS
PC boards are available to assist in the initial evaluation of
circuit performance using the OPA3680. They are available
free as an unpopulated PC board delivered with descriptive
documentation. The summary information for the boards is
shown below:
Contact the Burr-Brown Applications support line
(1-800-548-6132) to request this board (ask for the desired
literature number).
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 Video and
RF amplifier circuits where parasitic capacitance and induc-
tance can have a major effect on circuit performance. A
SPICE model for the OPA680 is available through either the
Burr-Brown Internet web page (http://www.burr-brown.com).
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 har-
monic distortion, temperature performance or dG/d charac-
teristics. These models do not attempt to distinguish be-
tween the package types in their small-signal AC perfor-
mance.
PRODUCT
OPA3680E
OPA3680U
1/3
R
49.9
R
16-Lead SSOP
PACKAGE
SO-16
OPA3680
1/3
Q
R
C
P
R
DEM-OPA368xE
DEM-OPA368xU
NUMBER
BOARD
PART
V
OUT
LITERATURE
REQUEST
NUMBER
MKT-354
MKT-364