December 25, 2024 
Professional magazine and portal dedicated to electronics 
ams OSRAM has launched the TOPLED® D5140, SFH 2202, a photodiode that offers improved performance compared to existing standard photodiodes, including higher sensitivity to visible light in the green part of the spectrum, and increased linearity.
These improved features enable smart watches, activity trackers and other wearable devices to measure heart rate and blood oxygen saturation (SpO2) more accurately, by substantially reducing the effect of interference from ambient light, and improving the quality of the received optical signal.
Benefiting from various optimizations of the process technology with which the photodiode die is fabricated, the TOPLED® D5140, SFH 2202 achieves 30 times higher linearity in the infrared spectrum than standard photodiodes, according to ams OSRAM internal benchmarking. Laboratory characterization also shows substantially increased sensitivity at the green wavelength used for heart rate measurement in photoplethysmography (PPG) – a technique that tracks the peaks and troughs of light absorption by blood vessels (more info).
