A safety package containing the photodiodes is provided for their protection. When photodiodes are continuously reverse-biased, the maximum voltage they can withstand is 50V. A photodiode has a pin number of 2. There was the possibility that photodiodes in a circuit would emit 100mW heat. When photodiodes operate, they should not be subjected to temperatures higher than 85°C. It should be noted that the photodiodes should be operated at -40°C as a minimum operating temperature. The reverse anode voltage for the photodiodes should be 50V. In general, the maximum heat generated by photodiodes should be 100mW in a circuit. With the reverse voltage of 50V, the photodiodes in the DC circuit can work properly. The current in a photodiode is 50nA even when there is no light input.