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.