Patent ID: 6518820
Filing Date: 2003-02-11
Classification: H03K

Abstract:
A touch contact switch circuit arrangement having at least one sensor element, wherein a control signal with an operating frequency is applied to said sensor element and is variable according to the operating state of said sensor element, said sensor element being operated by the approach or application of a finger, comprising:a signal source for producing said control signal, wherein said control signal is an alternating current signal; at least one of a filter and a voltage divider; a transistor, said control signal being applied across at least one of said filter and said voltage divider to a base of said transistor; a resistor ensuring a minimum base current at said transistor; and a collector of said transistor applied across a capacitor to ground; wherein an output signal at said transistor collector is tapped; wherein said sensor element is connected between said transistor base and ground; wherein said sensor element is a capacitive sensor element having a first capacitor plate applied to a dielectric material; wherein a contact surface is formed by applying a finger of a user to the dielectric material; wherein said contact surface forms a second capacitor plate; and whereby said second capacitor plate is connected to ground via the user.