Patent ID: 7969166

Claim:
A circuit for detecting the position or presence of an object in an observation area, the circuit comprising: a sensor electrode assembly comprising a first electrode forming part of a capacitor system whose capacitance to a reference potential is dependent on the presence or position of objects in an observation area bordered by the first electrode, an LC network coupled to the capacitor system and including a parallel-connected inductor and capacitor forming a resonant circuit having a parallel resonance frequency, a gyrator establishing a predetermined inductivity of the LC network, and an operational amplifier and a feedback capacitor feeding back a potential of the resonant circuit, a generator for applying an exciter frequency to the first electrode and the LC network at a frequency within the range of the parallel resonance frequency of the LC network, and evaluating means coupled to the sensor electrode for tracking resonance behavior of the LC network in capacitance changes of the detection capacitor system including the sensor electrode.