Circuit arrangement having a capacitive sensor element for a touch contact switch

The invention relates to a circuit arrangement for at least one sensor element of at least one touch contact switch, particularly operating on a capacitive basis. A control signal having a specific operating frequency is applied to the sensor element and is modified as a function of the operating state of the sensor element. The sensor element can e.g. be operated by the approach or application of a finger, which is intended to represent a switching signal. This switching signal is detected and evaluated by the circuit arrangement and is transmitted to further switching devices. The invention in one embodiment provides a circuit arrangement for a sensor element of a contact switch, in which a high frequency control signal () is applied to the sensor element (). The circuit arrangement () has a signal source () for the control signal (), a transistor (T), to whose base (B) is applied across a pass filter (RC) and a voltage divider (C) the control signal (), a resistor (R) applied to ground () ensuring a certain base current, the transistor collector (C), to which the output signal () is applied, is connected to ground across a capacitor (C), whilst between the transistor base (B) and ground is located a capacitive sensor element (). A preferred application field of the invention is a touch contact switch of a glass ceramic hotplate of an electric cooker.