Constant current circuit

A constant current circuit, comprising:

• a first insulated gate field effect transistor of a first conductivity type;
• a second insulated gate field effect transistor of a second conductivity type connected in series with said first insulated gate field effect transistor;
• a third insulated gate field effect transistor of the first conductivity type having a threshold voltage different from that of said first insulated gate field effect transistor;
• a forth insulated gate field effect transistor of the second conductivity type connected in series with said third insulated gate field effect transistor and having a threshold voltage equal to that of said second insulated gate field effect transistor;
• the series transistor pair of said first and second insulated gate field effect transistors being connected in parallel with the series transistor pair of said third and fourth insulated gate field effect transistor with said first and third insulated gate field effect transistors connected together and said second and fourth field effect transistors connected together;
• first means for electrically connecting the respective gate electrodes of said first and third insulated gate field effect transistors to the node between said third and fourth insulated gate field effect transistors;
• second means for electrically connecting the respective gate electrodes of said second and fourth insulated gate field effect transistor to the node between said first and second insulated gate field effect transistors;
• and
• a fifth insulated gate field effect transistor having a gate electrode connected to a respective one of said nodes so as to flow therethrough in operation a substantially constant current when a supply voltage is applied across the pair of parallel connected series transistor pairs and said fifth insulated gate field effect transistor is connected in parallel with the supply voltage.