Patent ID: 7129712

Claim:
An electrical circuit for determining a capacitance, comprising: a first device having a first terminal and a second terminal, wherein the first device has a first unknown capacitance and the first terminal is configured to receive a time-varying voltage signal; a rectifying circuit having an input terminal, an output terminal and a feedback terminal, wherein the input terminal is coupled to the second terminal and the output terminal is configured for coupling to an output electrical circuit, wherein the rectifying circuit is a switched capacitor circuit including a first switching mechanism and a second switching mechanism and wherein the first switching mechanism substantially conducts current and the second switching mechanism substantially blocks current for a first pre-determined duration of time, and the first switching mechanism substantially blocks current and the second switching mechanism substantially conducts current for a second pre-determined duration of time, and wherein the output electrical circuit is a switched capacitor circuit including a third switching mechanism and a fourth switching mechanism, and wherein the third switching mechanism substantially conducts current and the fourth switching mechanism substantially blocks current for a third pre-determined duration of time, and the third switching mechanism substantially blocks current and the fourth switching mechanism substantially conducts current for a fourth pre-determined duration of time; and a feedback circuit, wherein the feedback circuit selectively couples the output terminal to the input terminal using the feedback terminal such that the output terminal and the input terminal are substantially at a common voltage.