FEATURES
OVER 250kHz TRANSIMPEDANCE
BANDWIDTH
DYNAMIC RANGE: 5 Decades
EXCELLENT LONG-TERM STABILITY
LOW VOLTAGE NOISE: 10nV/√Hz
BIAS CURRENT: 3pA
OFFSET VOLTAGE: 25μV (max)
OFFSET DRIFT: 0.1μV/°C (max)
GAIN BANDWIDTH: 18MHz
QUIESCENT CURRENT: 800μA
FAST OVERLOAD RECOVERY
SUPPLY RANGE: 2.7V to 5.5V
SINGLE AND DUAL VERSIONS
MicroPACKAGE: DFN-8, MSOP-8

APPLICATIONS
PRECISION I/V CONVERSION
PHOTODIODE MONITORING
OPTICAL AMPLIFIERS
CAT-SCANNER FRONT-END
PHOTO LAB EQUIPMENT

DESCRIPTION
The OPA381 family of transimpedance amplifiers provides
18MHz of Gain Bandwidth (GBW), with extremely high
precision, excellent long-term stability, and very low 1/f noise.
The OPA381 features an offset voltage of 25μV (max), offset
drift of 0.1μV/°C (max), and bias current of 3pA. The OPA381
far exceeds the offset, drift, and noise performance that
conventional JFET op amps provide.
The signal bandwidth of a transimpedance amplifier depends
largely on the GBW of the amplifier and the parasitic
capacitance of the photodiode, as well as the feedback
resistor. The 18MHz GBW of the OPA381 enables a transimpedance
bandwidth of > 250kHz in most configurations.
The OPA381 is ideally suited for fast control loops for power
level measurement on an optical fiber.
As a result of the high precision and low-noise characteristics
of the OPA381, a dynamic range of 5 decades can be
achieved. This capability allows the measurement of signal
currents on the order of 10nA, and up to 1mA in a single I/V
conversion stage. In contrast to logarithmic amplifiers, the
OPA381 provides very wide bandwidth throughout the full
dynamic range. By using an external pulldown resistor to
–5V, the output voltage range can be extended to include 0V.
The OPA381 and OPA2381 are both available in MSOP-8
and DFN-8 (3mm x 3mm) packages. They are specified
from –40°C to +125°C.