Current DAC

A method of supplying a controllable current, comprising:

• providing a current DAC having a current reference circuit having a feedback node, a switchable resistor network that is communicably coupled to the feedback node of the current reference circuit via a first feedback network, and a current mirror having an output node communicably coupled to the switchable resistor network via a second feedback network;
• equalizing a first voltage between the feedback node and a voltage node with a second voltage across the switchable resistor network;
• and
• equalizing an output current that flows from the output node with an input current that flows into the switchable resistor network.

A current digital-to-analog converter (DAC) comprising:

• a current reference having an input coupled to a voltage source terminal and an output;
• a reference resistor having a first terminal coupled to the output of the current reference and a second terminal coupled to a voltage node;
• a first error amplifier having an inverting input coupled to the first terminal of the reference resistor, a non-inverting input, and an error output;
• a switchable resistor network having a current input coupled to the non-inverting input of the first error amplifier and a current output coupled to the voltage node;
• a first FET having a drain coupled to the first terminal of the switchable resistor network, a source and a gate;
• a second FET having a drain coupled to the source of the first FET, a gate coupled to the error output of the first error amplifier, and a source;
• a third FET having a drain that is an output for an output current, a gate coupled to the gate of the second FET and a source;
• and
• a second error amplifier having an inverting input coupled to the drain of the third FET, a non-inverting input coupled to the drain of the second FET, and an error output coupled to the gate of the first FET.