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Object sensing

  • US 7,560,938 B2
  • Filed: 04/28/2004
  • Issued: 07/14/2009
  • Est. Priority Date: 05/07/2003
  • Status: Active Grant
First Claim
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1. An electric field object sensing system, comprising:

  • a transmitter electrode;

    a receiver electrode;

    a charge pumping circuit coupled to the receiver electrode;

    an alternating voltage source coupled to the transmitter electrode and the charge pumping circuit; and

    an output connection coupled to the receiver electrode;

    wherein the charge pumping circuit is arranged to perform charge pumping according to the common cycle of alternating voltages applied from the alternating voltage source to the transmitter electrode and the charge pumping circuit; and

    the charge pumping circuit comprises a capacitor arranged such that a voltage developed across the capacitor saturates at a level dependent upon a capacitance between the transmitter electrode and the receiver electrode.

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