Patent ID: 7903011

Claim:
A sigma-delta digital-to-analog converter (SD DAC) comprising: a low pass filter comprising first and second inputs; first and second resistances each having first and second terminals, wherein the first terminals of the first and second resistances are respectively coupled to the first and second inputs of the low pass filter, and wherein the second terminals of the first and second resistances are respectively coupled together at a common node; a current supply; and a switching network for supplying current from the current supply to the first and second resistances, wherein the current supply and the first and second resistances operate to generate a first voltage and a second voltage at the first and second inputs of the low pass filter, wherein the current supply comprises: a first operational amplifier and a second operational amplifier; a first and second p-type transistor, wherein the first and second p-type transistors are coupled, and wherein the first p-type transistor is coupled to an output of the first operational amplifier; an n-type transistor, wherein the n-type transistor is coupled to an output of the second operational amplifier; and a current mirror, wherein the current mirror is coupled to the n-type transistor, wherein the first and second p-type transistors generate a first and second current, and wherein the current mirror generates a third current based on the first current.