FEATURES

BANDWIDTH

APPLICATIONS

1M

Ω

R

F

100k

Ω

+5V

7

2

3

4

6

OPA381

65pF

75pF

C

DIO DE

−5V

R

P

(Optional

Pulldown

Resistor)

VOUT

(0V to 4.4V)

Photodiode

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 25

µV (max), offset

drift of 0.1

µV/°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 trans-

impedance 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.

OPA381 RELATED DEVICES

PRODUCT

FEATURES

OPA380

90MHz GBW, 2.7V to 5.5V Supply

Transimpedance Amplifier

OPA132

16MHz GBW, Precision FET Op Amp

±15V

OPA300

150MHz GBW, Low-Noise, 2.7V to 5.5V Supply

OPA335

10

µV VOS, Zero-Drift, 2.5V to 5V Supply

OPA350

500

µV VOS, 38MHz, 2.5V to 5V Supply

OPA354

100MHz GBW CMOS, RRIO, 2.5V to 5V Supply

OPA355

200MHz GBW CMOS, 2.5V to 5V Supply

OPA656/7

230MHz, Precision FET,

±5V

OPA381

OPA2381

SBOS313B − AUGUST 2004 − REVISED NOVEMBER 2004

Precision, Low Power, 18MHz

Transimpedance Amplifier

PRODUCTION DATA information is current as of publication date. Products

conform to specifications per the terms of Texas Instruments standard warranty.

Production processing does not necessarily include testing of all parameters.

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 2004, Texas Instruments Incorporated

All trademarks are the property of their respective owners.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of Texas Instruments

semiconductor products and disclaimers thereto appears at the end of this data sheet.