OPA2381 Datasheet, PDF (14/19 Pages) Burr-Brown (TI) – Precision, Low Power, 18MHz Transimpedance Amplifier

OPA381
OPA2381
SBOS313B − AUGUST 2004 − REVISED NOVEMBER 2004
C_F
R_F
OPA 381
100Ω
1nF
ADS8325
RC values shown are optimized for the
ADS8325  values may vary for other ADCs.
Figure 13. Driving 16-Bit ADCs
INVERTING AMPLIFIER
Its excellent dc precision characteristics make the
OPA381 also useful as an inverting amplifier. Figure 14
shows it configured for use on a single-supply set to a
gain of 10.
C_F
R₁
100kΩ
R₂
10kΩ
V_IN
V_BIAS
V+
OPA381
V_OUT =
V_BIAS −
R₂
R₁
x V_IN
Figure 14. Inverting Gain
PRECISION INTEGRATOR
With its low offset voltage, the OPA381 is well-suited for
use as an integrator. Some applications require a
means to reset the integration. The circuit shown in
Figure 15 uses a mechanical switch as the reset
mechanism. The switch is opened at the beginning of
the integration period. It is shown in the open position,
which is the integration mode. With the values of R₁ and
C₁ shown, the output changes −1V/s per volt of input.
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R₁
1MΩ
V_IN
SW1
C₁
1µF
V+
1µF
V_BIAS
OPA381
V_OUT
Figure 15. Precision Integrator
DFN (DRB) THERMALLY-
ENHANCED PACKAGE
One of the package options for the OPA381 and
OPA2381 is the DFN-8 package, a thermally-enhanced
package designed to eliminate the use of bulky heat
sinks and slugs traditionally used in thermal packages.
The absence of external leads eliminates bent-lead
concerns and issues.
Although the power dissipation requirements of a given
application might not require a heat sink, for mechanical
reliability, the exposed power pad must be soldered to
the board and connected to V− (pin 4). This package
can be easily mounted using standard PCB assembly
techniques. See Application Note SLUA271, QFN/SON
PCB Attachment, located at www.ti.com. These DFN
packages have reliable solderability with either SnPb or
Pb-free solder paste.
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