Abstract: Systems and methods for providing power to a light source of a physiological system and for generating a desired signal. The physiological system may comprise a light drive circuit that may provide a digital signal to the light source of the physiological system. The digital signal may comprise a plurality of pulses. The plurality of pulses may include one or more features that may be adjustable to vary the power provided to the light source. For example, the pulses may have a varying width. The light drive circuit may be configured to provide power to the light source during each pulse of the plurality of pulses. The system may further comprise a front end circuit configured to receive the light generated by the light source in response to the plurality of pulses, where the light is attenuated by a body tissue of a patient. The front end circuit may comprise a response time.