Patent ID: 6075405
Filing Date: 2000-06-13
Classification: G05F

Abstract:
A constant current circuit comprising:a first field effect transistor having a drain connected to a first power supply via a first resistor, anda second field effect transistor having a drain connected to a gate of said first field effect transistor and to a second power supply via a second resistor and having a source and a gate connected to said first power supply, whereinthe resistance r.sub.2 of the second resistor satisfies a first condition, r.sub.2 =1/(W.sub.2 .multidot.(gm-gd)), in which W.sub.2 is the gate width of said second field effect transistor, gm is the transmission conductance per unit gate width of said first and second field effect transistors, and gd is the drain conductance per unit gate width of said first and second field effect transistors,the gate voltage Vg of said first field effect transistor satisfies a second condition, minimum saturation voltage of said second field effect transistor.ltoreq.Vg.ltoreq.minimum drain-source breakdown voltage of said second field effect transistor, andthe resistance r.sub.1, of the first resistor satisfies a third condition, r.sub.1 .multidot.I .sub.d1 =Vg, in which I .sub.d1 is the drain current flowing in said first field effect transistor.