Methods and circuits for providing a minimum driving voltage to a current-driven load (such as a laser diode) are disclosed. The circuit and methods may be useful for efficiently providing a bias and/or driving current to the current-driven load with minimal energy loss. The circuit generally comprises (1) a driver or voltage source configured to provide the bias and/or driving current to the current-driven load, (2) a sense circuit configured to (i) sense the bias and/or driving current and (ii) convert the bias and/or driving current to a first voltage, and (3) a comparator configured to (i) receive the first voltage and first and second reference voltages and (ii) provide a feedback/error signal to the driver or voltage source, the feedback/error signal configured to maintain or adjust the bias and/or driving current at or towards a target value.