Optical sensor device and electronic apparatus

An optical sensor device comprising:

• an optical sensor element;
• and
• a current mirror circuit comprising at least first, second, and third thin film transistors,
• wherein a first electrode of the optical sensor element is electrically connected to each of a first region of the first thin film transistor and a gate of the first thin film transistor,
• wherein a second electrode of the optical sensor element is electrically connected to each of a first region of the second thin film transistor, a first region of the third thin film transistor, and a terminal,
• wherein a second region of the first thin film transistor is electrically connected to each of a second region of the second thin film transistor and a second region of the third thin film transistor,
• wherein the gate of the first thin film transistor is electrically connected to each of a gate of the second thin film transistor and a gate of the third thin film transistor,
• wherein each gate length of the first, second, and third thin film transistor are equal,
• wherein each channel width of the first, second, and third thin film transistor are equal,
• wherein the amount of current flowing into the terminal is pronortional to the number of thin film transistors in the current mirror circuit, and
• wherein the optical sensor element and the current mirror circuit are formed over a substrate.