Signal processing apparatus, filter apparatus, signal processing method and filtering method

A filter apparatus, wherein different variable capacitors sample input signals in sequence and at least a portion of a charge held in a number of variable capacitors after sampling is outputted to a rear stage capacitor which can be electrically connected to the number of variable capacitors, comprising:

• a switching portion for switching the circuit mode between a sampling mode, in which the input signals are sampled by the variable capacitors, a holding mode in which a charge gained by sampling the input signals is held in the variable capacitor, and an output mode, in which a charge held by the variable capacitor is outputted, and
• the variable capacitors includes
• an input terminal through which the input signals are inputted in the sampling mode, and
• a control terminal to which a first control signal which decreases the capacitance of the variable capacitor to a value below the capacitance in the sampling mode is inputted in the output mode, and a second control signal having a predetermined reference voltage is inputted in the holding mode, where an insulating layer is provided between the control terminal and the input terminal.

A signal processing method, comprising the steps of:

• inputting an input signal through an input terminal of a variable capacitor of which the capacitance is variable and making the variable capacitor sample the input signal;
• holding a charge gained by sampling the input signal in the variable capacitor;
• and
• outputting the charge held in the variable capacitor, wherein
• in the outputting step, a first control signal for lowering the capacitance of the variable capacitor to a value beneath the capacitance in the sampling step is inputted through a control terminal of the variable capacitor which is arranged on the surface facing the input terminal via an insulating layer, and
• in the holding step, a second control signal having a predetermined reference voltage is inputted through a control terminal of the variable capacitor.

A filtering method, comprising the steps of:

• inputting input signals through input terminals of different variable capacitors in sequence and sampling the input signals in the variable capacitors;
• holding a charge gained by sampling the input signals in the respective variable capacitors;
• and
• outputting the charge held in two or more of the variable capacitors to a rear stage capacitor which is provided in a rear stage, wherein
• in the output step, a first control signal which decreases the capacitance of the variable capacitors to a value below the capacitance in the sampling step is inputted through a control terminal of the variable capacitors which are arranged on the side facing the input terminal via an insulating layer, and
• in the holding step, a second control signal having a predetermined reference voltage is inputted through a control terminal of the variable capacitor.