a constant current circuit including a first field effect transistor having a drain connected to an output terminal and having a source connected to a first power supply via a first resistor , and a plurality of field effect transistors , of each of which the ordinal number is 1 through n , and of each of which the source and the drain are connected to each other , and each of which is connected in series to one another to form a series circuit of field effect transistors , a drain of a field effect transistor located at an end of the series circuit of field effect transistors being connected to a second power supply via a second resistor , a drain of one field effect transistor composing the series circuit of field effect transistors being connected to a gate of said first field effect transistor , and an opposite end of the series circuit of field effect transistors being connected the first power supply terminal .