Some embodiments described herein are directed to a photo sensor and a method of operating a photo sensor. In an embodiment, a photo sensor comprises a photo diode, a filter circuit, and an output circuit. The filter circuit has an input node configured to be electrically coupled to an output node of the photo diode, and has an output node. The filter circuit has an adjustable gain, and the adjustable gain is adjustable based on a signal output from the filter circuit. The output circuit has an input node configured to be electrically coupled to the output node of the filter circuit.