| 主权项 |
1. A capacitive sensing device, comprising
an antenna electrode configured for emitting an alternating electric field in response to an alternating voltage caused in the antenna electrode and a control and evaluation circuit that includes
a transimpedance amplifier configured to maintain the alternating voltage equal to an alternating reference voltage on a reference voltage node by injecting a current into the antenna electrode and to measure the current,a microcontroller,and a multiplexer configured and arranged to switch said antenna electrode alternately to a current input of the transimpedance amplifier and to the alternating reference voltage node, wherein the microcontroller is configured to control the multiplexer with a digital control signal, wherein the multiplexer and the transimpedance amplifier and a low-pass filter operatively connected to the transimpedance amplifier form together a synchronous rectifier arrangement, and wherein the current input node of the transimpedance amplifier is AC-coupled to the reference voltage node by a protection capacitor. |
