Systems and methods for sensing temperature on a chip are described herein. In one embodiment, a temperature sensor comprises a first transistor having a gate, a second transistor having a gate coupled to the gate of the first transistor, and a bias circuit configured to bias the gates of the first and second transistors such that the first and second transistors operate in a sub-threshold region, and to generate a current proportional to a difference between a gate-to-source voltage of the first transistor and a gate-to-source voltage of the second transistor. The temperature sensor also comprises an analog-to-digital converter (ADC) configured to convert the current into a digital temperature reading.