Patent ID: 7466145

Claim:
A voltage measuring apparatus that measures a voltage of a measured object, comprising: a detection electrode capable of being disposed facing the measured object; a variable capacitance circuit that is connected between the detection electrode and a reference potential and whose electrostatic capacitance can be changed; a voltage generating circuit that generates the reference potential; and a control unit, wherein the control unit causes the voltage generating circuit to change a voltage of the reference potential while the electrostatic capacitance of the variable capacitance circuit is being changed, wherein the variable capacitance circuit includes first and second capacitance circuits that are each constructed by connecting a first element, which has a P-type semiconductor and an N-type semiconductor that are joined together, and a DC power supply, which applies a reverse bias to the first element, in series, the first and second capacitance circuits being disposed in series between the detection electrode and the reference potential so that respective directions of the first elements become reverse to each other, and a driving circuit that drives the variable capacitance circuit by applying driving signals with inverted phases to the first and second capacitance circuits, respectively.