Systems, methods, and devices for improved patient monitor signal processing with higher signal-to-noise ratio (SNR) are provided. In accordance with an embodiment, an electronic patient monitor may include drive circuitry, a current-to-voltage converter, and feedback circuitry. The drive circuitry may drive an emitter of a medical sensor with dark periods during which the emitter does not emit light, and the current-to-voltage converter may receive and amplify a photocurrent signal from a detector of the sensor. The feedback circuitry may provide a feedback signal to the current-to-voltage converter. The feedback signal, based at least in part on the output of the current-to-voltage converter during the dark periods, may cause the current-to-voltage converter to substantially exclude an ambient light component of the photocurrent. As a result, the current-to-voltage converter may employ a higher transimpedance without distorting the output voltage signal due to oversaturation, and thus may achieve a higher SNR.
