Method and apparatus for field-effect transistor current sensing using the voltage drop across drain to source resistance that eliminates dependencies on temperature of the field-effect transistor and/or statistical distribution of the initial value of drain to source resistance

An apparatus comprising:

• a first FET comprising a gate, a source, and a drain, wherein the gate of the first FET is configured to receive a first voltage, and wherein the source of the first FET is configured to be coupled to ground;
• a second FET comprising a gate, a source, and a drain, wherein the gate of the second FET is configured to receive the same voltage, and wherein the source of the second FET is configured to be coupled to ground;
• a circuit comprising first and second input nodes coupled to the drains of the first and second FETs, respectively, the circuit is configured to generate a signal as a function of a voltage measured at the drain of the first FET with respect to ground, wherein the signal is proportional to a current flowing into or out of the drain of the first FET.

An apparatus comprising:

• a first FET comprising a gate, a source, and a drain, wherein the gate of the first FET is configured to receive a first voltage, and wherein the source of the first FET is coupled to a first node;
• a second FET comprising a gate, a source, and a drain, wherein the gate of the second FET is configured to receive the same voltage, and wherein the source of the second FET is coupled to a second node;
• a circuit comprising first and second input nodes coupled to the drains of the first and second FETs, respectively, the circuit is configured to generate a signal as a function of a voltage measured at the drain of the first FET with respect to ground, wherein the signal is proportional to a current flowing into or out of the drain of the first FET.