Patent ID: 9075486
Filing Date: 2015-07-07
Classification: G01D,G01R,G06F,H03F

Abstract:
1. A circuit for sensing a capacitance between a first electrode and a second electrode, comprising: a switching circuit connected to the first electrode, controlled to change a voltage level of the first electrode; a transconductance amplifier mirror circuit including a first output port and a second output port, the first output port being controlled to connect to the second electrode, the transconductance amplifier mirror circuit being operative to maintain a voltage level of the first output port at a reference voltage, wherein when the voltage level of the first output port decreases, the transconductance amplifier mirror circuit supplies a first amount of charges to the first output port and a second amount of charges to the second output port responsive to a difference between a voltage level of the second electrode and the reference voltage; and a charge calculation circuit connected to the second output port of the transconductance amplifier mirror circuit, operative to generate a sensed signal responsive to the second amount of charges; wherein the second amount of charges is proportional to the first amount of charges.