The OPA380 family of transimpedance amplifiers provides high-speed (90MHz Gain Bandwidth [GBW]) operation, with extremely high precision, excellent long-term stability, and very low 1/f noise. It is ideally suited for high-speed photodiode applications. The OPA380 features an offset voltage of 25μV, offset drift of 0.1μV/°C, and bias current of 50pA. The OPA380 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 90MHz GBW of the OPA380 enables a transimpedance bandwidth of > 1MHz in most configurations. The OPA380 is ideally suited for fast control loops for power level on an optical fiber.

As a result of the high precision and low-noise characteristics of the OPA380, a dynamic range of 4 to 5 decades can be achieved. For example, this capability allows the measurement of signal currents on the order of 1nA, and up to 100μA in a single I/V conversion stage. In contrast to logarithmic amplifiers, the OPA380 provides very wide bandwidth throughout the full dynamic range. By using an external pull-down resistor to -5V, the output voltage range can be extended to include 0V.

The OPA380 (single) is available in MSOP-8 and SO-8 packages. The OPA2380 (dual) is available in the miniature MSOP-8 package. They are specified from -40°C to +125°C.