OPA380 Datasheet, PDF (9/22 Pages) Burr-Brown (TI) – Precision, High-Speed Transimpedance Amplifier

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APPLICATIONS INFORMATION
BASIC OPERATION
The OPA380 is a high-performance transimpedance
amplifier with very low 1/f noise. As a result of its unique
architecture, the OPA380 has excellent long-term input
voltage offset stability—a 300-hour life test at 150°C
demonstrated randomly distributed variation
approximately equal to measurement repeatability of
1µV.
The OPA380 performance results from an internal
auto-zero amplifier combined with a high-speed
amplifier. The OPA380 has been designed with circuitry
to improve overload recovery and settling time over a
traditional composite approach. It has been specifically
designed and characterized to accommodate circuit
options to allow 0V output operation (see Figure 3).
The OPA380 is used in inverting configurations, with the
noninverting input used as a fixed biasing point.
Figure 1 shows the OPA380 in a typical configuration.
Power-supply pins should be bypassed with 1µF ceramic
or tantalum capacitors. Electrolytic capacitors are not
recommended.
C_F
R_F
+5V
1µF
λ
OPA380
V_OUT(1)
(0.5V to 4.4V)
V_BIAS = 0.5V
NOTE: (1) V_OUT = 0.5V in dark conditions.
Figure 1. OPA380 Typical Configuration
OPA380
OPA2380
SBOS291G − NOVEMBER 2003 − REVISED SEPTEMBER 2007
OPERATING VOLTAGE
The OPA380 series op amps are fully specified from
2.7V to 5.5V over a temperature range of −40°C to
+125°C. Parameters that vary significantly with operat-
ing voltages or temperature are shown in the Typical
Characteristics.
INTERNAL OFFSET CORRECTION
The OPA380 series op amps use an auto-zero topology
with a time-continuous 90MHz op amp in the signal
path. This amplifier is zero-corrected every 100µs using
a proprietary technique. Upon power-up, the amplifier
requires approximately 400µs to achieve specified V_OS
accuracy, which includes one full auto-zero cycle of
approximately 100µs and the start-up time for the bias
circuitry. Prior to this time, the amplifier will function
properly but with unspecified offset voltage.
This design has virtually no aliasing and very low noise.
Zero correction occurs at a 10kHz rate, but there is very
little fundamental noise energy present at that
frequency due to internal filtering. For all practical
purposes, any glitches have energy at 20MHz or higher
and are easily filtered, if required. Most applications are
not sensitive to such high-frequency noise, and no
filtering is required.
INPUT VOLTAGE
The input common-mode voltage range of the OPA380
series extends from V− to (V+) – 1.8V. With input
signals above this common-mode range, the amplifier
will no longer provide a valid output value, but it will not
latch or invert.
INPUT OVERVOLTAGE PROTECTION
Device inputs are protected by ESD diodes that will
conduct if the input voltages exceed the power supplies
by more than approximately 500mV. Momentary
voltages greater than 500mV beyond the power supply
can be tolerated if the current is limited to 10mA. The
OPA380 series feature no phase inversion when the
inputs extend beyond supplies if the input is current
limited.
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