Abstract: Systems and methods are provided for shaping drive pulses in a medical device. In some embodiments, signal channel characteristics introduce undesirable channel effects including signal distortions such as droop in a square wave pulse. In some embodiments, the system may shape light drive pulses to compensate for channel effects. Light drive characteristics may be determined based on, for example, modeling of components and/or iterative calibration techniques. The output of the channel may be used to determine physiological information such as blood oxygen saturation and respiration rate.