Photodiode Signal & Noise Calculator
Calculate photocurrent, output voltage, bandwidth, noise, and NEP for load-resistor and TIA readout configurations.
A photodiode converts optical power to photocurrent (I = R·P, where R is responsivity in A/W). The readout circuit determines bandwidth, noise floor, and signal-to-noise ratio. This calculator covers two common configurations: load-resistor (simple, high bandwidth at low resistance, high noise) and transimpedance amplifier (TIA, high gain-bandwidth product, low noise at moderate bandwidth). For each configuration it computes photocurrent, output voltage, 3 dB bandwidth, shot noise, thermal (Johnson) noise, total noise, signal-to-noise ratio, and noise-equivalent power (NEP). Use this tool when designing a photodetection circuit or selecting a load resistance for a given signal level and bandwidth requirement.