US Patent 9965056 Active stylus and control circuit thereof

The present disclosure provides systems and methods for receiving an input signal from a touch-sensitive interface via a first electrode associated with a tip of an active stylus. An input signal may be amplified via a control circuit that adjusts the gain of one or more amplifiers to compensate for changes in tip capacitance between the tip of the active stylus and the touch-sensitive interface. Changes in tip capacitance may be indirectly detected and compensated for by comparing the tip capacitance with that of a reference capacitor via a differential amplification circuit that includes one or more differential amplifiers.