METHOD AND APPARATUS FOR DRAIN SWITCHING WITH REPLICATION LOOP FOR FAST LED TURN ON TIME

A method and apparatus for current drain switching with a replica loop. The method comprises the steps of: matching a voltage across a current sense resistor with a voltage created by a reference current across a matched reference resistor; replicating an operating point of an output transistor using a scaled matched replica of the output transistor and the current sense resistor. The method then shifts a feedback voltage from the output sense resistor to the matched replica sensor and shifts the output of a gate from an output transistor to the replica transistor. A first switch is then actuated in order to preserve the gate charge of the output transistor. A second switch is actuated to sample and hold a drain voltage in the buffer in order to bias the drain of the replica transistor. The third switch is then activated to stop the output current.