The BPW21R is a Planar Silicon PN Photodiode is especially designed for high precision linear applications. Due to its extremely high dark resistance, the short circuit photocurrent is linear over seven decades of illumination level. On the other hand, there is a strictly logarithmic correlation between open circuit voltage and illumination over the same range. The device is equipped with a flat glass window with built in color correction filter, giving an approximation to the spectral response of the human eye.
