18 MHz transimpedance amplifier for photodiode front-ends
Its 18 MHz gain-bandwidth product and 12 V/µs slew rate support fast optical pulse detection, while the 3 pA input bias current and 7 µV input offset voltage minimize DC error in low-light measurements. Applications include optical sensors, medical diagnostics, and industrial photodetection chains.
3 pA input bias — why it matters for photodiode interfaces
In a transimpedance configuration, the input bias current flows through the feedback resistor, creating a DC offset voltage at the output. At 3 pA, the OPA381AIDGKR keeps this error negligible even with large feedback resistors used in low-light applications. Compare this to a general-purpose op-amp with nanoamp bias, which would swamp a small photocurrent signal. The 7 µV input offset voltage further tightens the baseline accuracy. For a photodiode producing 1 nA through a 1 MΩ feedback resistor, the signal is 1 mV — the offset contribution is less than 1% of that.
8-VSSOP package — footprint and layout notes
The small footprint suits space-constrained optical modules.