An active stylus having a control circuit configured to wake up the stylus from a sleep mode to an active mode in response to pressure applied to a tip of the stylus. The stylus includes a force sensor electrically coupled to a power source, an operational amplifier, and a voltage level comparator, the voltage level comparator configured to output a digital wake up interrupt signal when pressure is applied to the tip when the control circuit is in the sleep mode. The operational amplifier is configured to provide an analog signal representative of varying pressure on the tip. This signal is processed by the control circuit such that the stylus goes into the sleep mode after a specified period of time following cessation of variations in the analog signal.