Patent ID: 11954283
Assignee: TOUCH BIOMETRIX LIMITED
Field: Computer technology (Electrical engineering)
Classification: CPC G  H | IPC G  H

Claim 7:
8. A sensor array comprising a plurality of touch sensitive pixels, each pixel comprising:
a capacitive sensing electrode for accumulating a charge in response to proximity of a conductive object to be sensed;
a reference capacitor connected in series with the capacitive sensing electrode so that, in response to a control voltage, an indicator voltage is provided at the connection between the reference capacitor and the capacitive sensing electrode to indicate the proximity of the conductive object to be sensed;
a sense voltage controlled impedance, VCI, having a control terminal connected so that a voltage at the control terminal corresponds to the indicator voltage and so the impedance of the sense VCI is controlled by the indicator voltage, and wherein a conduction path of the sense VCI is connected to a readout line for providing readout signals to a readout circuit;
wherein each pixel is configured to receive a gate drive signal to activate the sense VCI of said pixel to output a current to its readout line, wherein the current output to the readout line will depend on the voltage at the control terminal of the sense VCI;
wherein each pixel comprises a reset circuit configured to set the control terminal of the sense VCI to a reset voltage prior to a gate drive signal being applied to said pixel, wherein the reset voltage is selected so that in response to the gate drive signal subsequently being applied to said pixel and a user's skin being in proximity to the capacitive sensing electrode of said pixel, a resulting voltage at the control terminal of the sense VCI will cause the sense VCI to operate in a linear region;
wherein the reset circuit comprises a reset VCI wherein a conduction path of the reset VCI is connected between a second plate of the reference capacitor and a first plate of the reference capacitor; and, wherein each pixel comprises a gate line VCI, and a conduction path of the gate line VCI connects the reference signal supply to the reference capacitor for providing the control voltage.