Patent ID: 8258821

Claim:
An apparatus comprising: a reference circuit; a level shifter that receives an input signal; a bipolar differential pair that is coupled to the reference circuit and the level shifter; a tail current source that is coupled to the bipolar differential pair, wherein the tail current sources a first current when the input signal is less than a first threshold; a switching circuit having a plurality of current branches, wherein each current branch is coupled to the bipolar differential pair, and wherein a first current branch of the plurality of current branches receives the input voltage, and wherein a first current branch is activated when the input signal become greater than the first threshold so as to source a second current through the differential bipolar pair, and wherein a second current branch of the plurality of current branches mirrors the second current when the input signal becomes greater than a second threshold, and wherein the first current branch is deactivated when the input signal becomes greater than a second threshold; and an output circuit that is coupled to the switching circuit.