A large area photodiode and current to frequency converter combined in a clear plastic 8-pin DIL package. The output is a pulse train whose frequency is directly proportional to the light intensity. The output is CMOS compatible (use a 3k3 pulldown resistor to drive LS TTL) and the frequency can be measured by pulse counting, period timing or integration techniques. The photodiode has a wide dynamic range, high sensitivity and high noise immunity. The output frequency range is determined by a capacitor in the range 10pf to 100pf, which permits the output frequency to fall within some suitable range for any given light intensity.