Patent ID: 7535286

Claim:
A constant current source apparatus for supplying a load current to at least one load, comprising: first and second output terminals, at least one of said first and second output terminals capable of being connected to said load; and first and second depletion-type MOS transistors connected in series between said first and second output terminals, wherein a source and a gate of said first depletion-type MOS transistor being connected to a gate of said second depletion-type MOS transistor, thereby to form said constant current source apparatus, and wherein said first and second depletion-type MOS transistors interact such that, when a voltage applied to said constant current source apparatus fluctuates, then said first and second depletion-type MOS transistors suppress a resulting fluctuation of said load current due to a channel length modulation effect, and wherein said channel-length modulation effect is thereby limited to be within the formula λ·(V thl -V th2 ), where: λ is a channel-length modulation factor of said first and second depletion-type MOS transistors; V th1 is a threshold voltage of said first depletion-type MOS transistor; and V th2 is a threshold voltage of said second depletion-type MOS transistor.