Patent ID: 7509058

Claim:
A data transmission apparatus for performing data communication based on optical transmission, comprising: a transmitting unit for converting electric communication data into, and sending electric communication data as, optical communication data; and a photoelectric conversion circuit for receiving said optical communication data and converting said optical communication data into received electric communication data, said photoelectric conversion circuit comprising: a light receiving unit for generating a current based on said optical communication data; a current supply for generating a reference current; and a signal generating unit for generating said received electric communication data based on said current generated by said light receiving unit, said data transmission apparatus further comprising: a variable setting unit for setting said photoelectric conversion circuit to generate received electric communication data in response to an input level of said optical communication data, said variable setting unit comprising: a variable current supply for setting said photoelectric conversion circuit by one of: adding to said reference current substantially half of said current generated by said light receiving unit when said optical communication data indicates H logic, adding to said reference current a substantial average of said current generated by said light receiving unit when said optical communication data indicates H logic and said current generated by said light receiving unit when said optical communication data indicates L logic, subtracting from said current generated by said light receiving unit substantially half of said current generated by said light receiving unit when said optical communication data indicates H logic, and subtracting from said current generated by said light receiving unit the substantial average of said current generated by said light receiving unit when said optical communication data indicates H logic and said current generated by said light receiving unit when said optical communication data indicates L logic.