Patent ID: 8334660

Claim:
A driving circuit for a light source, comprising: an input stage comprising a first transistor connected to a current source or a current sink and a first node between the first transistor and the current source or the current sink; an output stage comprising at least one second transistor for coupling to the light source and at least one second node between the second transistor and the light source; and a tracking component comprising a first input coupled to a first node in the input stage and a second input coupled to a second node in the output stage, the tracking component generating an output signal to control the first transistor and the at least one second transistor so that a voltage level of the first node tracks a voltage level of the second node, wherein the tracking component comprises an amplifier generating an output signal that increases as a voltage difference between the first node and the at least one second node increases, the output signal decreasing as a voltage difference between the first node and the at least one second node decreases; a first switch between the amplifier and a gate of the second transistor, the first switch turned on to receive the output signal from the amplifier in a control mode and turned off in a hold mode; and a second switch between the first transistor and the current sink or the current source, the second switch turned on in the control mode and turned off in the hold mode.