The ADL5315 is a wide input current range precision high-side current mirror featuring a stable and user-adjustable input voltage. It is optimized for use with PIN photodiodes, but its flexibility and wide operating range make it suitable for a broad array of additional applications. The part provides a compact solution for the common and often challenging problem of interfacing an optical power monitoring device (such as a log amp) to the cathode-side of a PIN photodiode. The ADL5315 mirrors the current at the cathode at a 1:1 ratio over a six-decade range, producing an output exactly proportional to the reference current monitored. Competing optical current monitors have much higher mirror ratios over narrower dynamic ranges, rendering proportional outputs at very low input currents impossible, while discrete solutions are more tedious to implement and may require significantly more board space.