A transmission device is provided. The transmission device includes a voltage generator, a convertor, a voltage buffer and a transmission element. The voltage generator generates a first voltage signal according to a first current. The convertor generates a second current using a source current proportional to a temperature, generates a third current according to the first voltage signal, and converts a sum of the second current and the third current to a second voltage signal. The voltage buffer generates a driving voltage proportional to the temperature according to the second voltage signal. The transmission element operates based on the driving voltage.