Stylus for capacitive touchscreen

Abstract

Embodiments of amplifiers and electrodes for capacitive styluses are disclosed. The amplifiers detect an input signal from a capacitive touch sensor, such as a touchscreen or touchpad, amplify and invert the signal, and emit the amplified and inverted signal to cause the capacitive touch sensor to detect a touch. The electrode sets, or tips, pair a sensing electrode and an emitting electrode, shielded from each other to limit interference, in a fine-point non-deforming configuration that improves usability over existing stylus tips.

What is claimed is: 
     
         1 . A circuit configured for actively interacting with a capacitive touch sensor, comprising:
 an input, electrically coupled to a sensing electrode;   an amplifier having a plurality of amplifier stages; and   an output, electrically coupled to an emitting electrode,   wherein the amplifier receives a signal from the input via the sensing electrode, inverts and amplifies the signal, and outputs the signal through the emitting electrode via the output, and   wherein the amplifier amplifies only a portion of the signal that exceeds a threshold voltage, by subjecting the signal through at least one level-setting element in each of the plurality of amplifier stages in the amplifier according to the threshold voltage.   
     
     
         2 . The circuit of  claim 1 , wherein the input is electrically coupled to ground through a varistor. 
     
     
         3 . The circuit of  claim 1 , wherein the output is electrically coupled to ground through a varistor. 
     
     
         4 . The circuit of  claim 1 , wherein the amplifier comprises at least one op-amp. 
     
     
         5 . The circuit of  claim 1 , wherein the plurality of amplifier stages comprises:
 a first amplification stage;   a second amplification stage;   a signal limiter; and   a driver stage,   wherein the amplifier receives a signal from the input via the sensing electrode, outputs the signal through the first amplification stage, to the second amplification stage, and then concurrently to the signal limiter, and driver stage, respectively, and then through the driver stage, to be output through the emitting electrode via the output.   
     
     
         6 . The circuit of  claim 5 , wherein the signal limiter is a fixed signal limiter. 
     
     
         7 . The circuit of  claim 5 , wherein the signal limiter is an adjustable signal limiter. 
     
     
         8 . The circuit of  claim 5 , wherein the first amplification stage, the second amplification stage, and the signal limiter are grounded to a first ground, and the driver stage is grounded to a second ground, and the first ground and second ground are electrically coupled through a resistor. 
     
     
         9 . The circuit of  claim 1 , wherein the plurality of amplifier stages comprises:
 a first amplification stage;   a second amplification stage;   a driver stage;   a regulator stage;   a comparator stage;   a final driver stage; and   an output mixer stage,   wherein the amplifier receives a signal from the input via the sensing electrode, outputs the signal through the first amplification stage, to the second amplification stage, and then concurrently to the driver stage and regulator stage, and comparator stage and final driver stage, respectively, wherein a regulator stage signal and a final driver stage signal is output to the output mixer stage and recombined to be output through the emitting electrode via the output.   
     
     
         10 . The circuit of  claim 9 , wherein the plurality of amplifier stages, the driver stage, the regulator stage, the comparator stage and the output mixer stage are grounded to a first ground, and the final driver stage is grounded to a second ground, and the first ground and second ground are electrically coupled through a resistor.