Patent ID: 7902912

Claim:
A bias current generator comprising: a first amplifier having an inverting input, a non-inverting input and an output; a first bipolar transistor having a base-emitter voltage associated with a first one of the inverting or non-inverting inputs of the first amplifier; a load MOS transistor comprising a gate, a source, and a drain, wherein the load MOS transistor is associated with a second one of the inverting or non-inverting inputs of the first amplifier, wherein the gate of the load MOS transistor is operatively coupled to the output of the first amplifier; a second bipolar transistor operating at a lower collector current density than that of the first bipolar transistor, wherein a base-emitter voltage of the second bipolar transistor is also associated with the second one of the inverting or non-inverting inputs of the first amplifier such that the base-emitter voltage of the second bipolar transistor is arranged in series with a drain-source voltage of the load MOS transistor; and a biasing MOS transistor associated with the load MOS transistor, wherein the gate of the biasing MOS transistor is operatively coupled to the output of the first amplifier such that a gate to source voltage of the load MOS transistor and a gate to source voltage of the biasing MOS transistor are the same; wherein the first amplifier, the first bipolar transistor, the second bipolar transistor, the load MOS transistor, and the biasing MOS transistor are arranged in a feedback loop such that the biasing MOS transistor is biased to operate in the saturation region and the load MOS transistor is biased to operate in the triode region; wherein the first and second bipolar transistors are arranged relative to the load MOS transistor such that operation of the feedback loop develops a voltage across the drain-source resistance r on of the load MOS transistor equivalent to the base-emitter voltage difference ΔV be between the first bipolar transistor and the second bipolar transistor thereby generating a PTAT bias current.