OPA2682 Datasheet, PDF (15/19 Pages) Burr-Brown (TI) – Dual, Wideband, Fixed Gain BUFFER AMPLIFIER With Disable

AC-COUPLED DIFFERENTIAL LOWPASS FILTER
The circuit in Figure 5 gives a single +5V supply, 3rd-
order Chebyshev lowpass filter with 0.5dB of ripple in the
passband and a –3dB bandwidth of 20MHz. This filter is
based on the KRC active filter topology, which uses an
amplifier with a fixed gain ≥ 1. The OPA2682 makes a
good amplifier for this type of filter. The component
values have been pre-distorted to compensate for the op
amp’s parasitic effects.
DESIGN-IN TOOLS
APPLICATIONS SUPPORT
The Burr-Brown Applications Department is available for
design assistance at 1-800-548-6132 (US/Canada only). The
Burr-Brown internet web page (http://www.burr-brown.com)
has the latest data sheets and other design aids.
DEMONSTRATION BOARDS
Two PC boards are available to assist in the initial evalua-
tion of circuit performance using the OPA2682 in its two
package styles. These are available free as an unpopulated
PC board delivered with descriptive documentation. The
summary information for these boards is shown in the table
below.
PRODUCT
OPA2682U
OPA2682N
PACKAGE
8-Lead SO-8
14-Lead SO-14
DEMO
BOARD
NUMBER
DEM-OPA268xU
DEM-OPA268xN
LITERATURE
REQUEST
NUMBER
MKT-352
MKT-353
Contact the Burr-Brown applications support line
(1-800-548-6132) to request any of these boards, using the
literature request 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 OPA2682 is available through 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/dφ char-
acteristics. These models do not attempt to distinguish
between the package types in their small-signal AC perfor-
mance.
OPERATING SUGGESTIONS
GAIN SETTING
Setting the gain with the OPA2682 is very easy. For a gain
of +2, ground the –IN pin and drive the +IN pin with the
signal. For a gain of +1, leave the –IN pin open and drive the
+IN pin with the signal. For a gain of –1, ground the +IN pin
and drive the –IN pin with the signal. Since the internal
resistor values change significantly over temperature and
process, external resistors should not be used to modify the
gain.
OUTPUT CURRENT AND VOLTAGE
The OPA2682 provides output voltage and current capabili-
ties that are unsurpassed in a low-cost, monolithic op amp.
Under no-load conditions at 25°C, the output voltage typi-
cally swings closer than 1V to either supply rail; the guar-
anteed swing limit is within 1.2V of either rail. Into a 15Ω
load (the minimum tested load), it is guaranteed to deliver
more than ±135mA.
0.10µF _51.1Ω
82pF
105Ω
205Ω
+5V _1.10kΩ
1kΩ
V_IN
180pF
1kΩ
0.10µF _{51.1Ω 105Ω}
0.10µF
18pF
1.10kΩ
205Ω
0.10µF
+5V
400Ω
1/2
OPA2682
400Ω
400Ω
400Ω
1/2
OPA2682
82pF
V_OUT
FIGURE 5. Single-Supply, 3rd-Order Differential Chebyshev Low-Pass Filter.
®
15
OPA2682