Low distortion circuit with switched capacitors

A switched capacitor circuit having circuit input and output terminals, comprising:

• an amplifier having an amplifier input terminal and an amplifier output terminal, said amplifier output terminal being the circuit output terminal;
• a first switch element having first and second switch terminals and a switch common terminal alternatively coupled to said first and second switch terminals of said first switch element, said first switch terminal of said first switch element being coupled to the circuit input terminal and said second switch terminal of said first switch element being coupled to said amplifier output terminal;
• a second switch element having first and second switch terminals and a switch common terminal alternatively coupled to said first and second switch terminals of said second switch element, said first switch terminal of said second switch element being coupled to said amplifier input terminal and said second switch terminal of said second switch element coupled to a first reference voltage;
• a first impedance element coupled between said switch common terminal of said first switch element and said switch common terminal of said second switch element;
• a second impedance element coupled between said switch common terminal of said first switch element and a second reference voltage;
• and
• first and second control signals controlling said first and second switch elements, respectively, and causing, said switch common terminal of said first switch element to be coupled to the circuit input terminal when said switch common terminal of said second switch element is coupled to said first reference voltage and causing said switch common terminal of said first switch element to be coupled to said amplifier output terminal when said switch common terminal of said second switch element is coupled to said amplifier input terminal wherein said switch common terminal of said first switch element is coupled to said circuit input terminal or said amplifier output terminal greater than one half the time.

A method of compensating for non-linear effects in a switched capacitor circuit switched at a predetermined frequency, the method comprising:

• connecting a first end of a first capacitor to a circuit node alternately connected, through a first switch circuit, to a circuit input and a first voltage reference, said circuit node having an intrinsic parasitic capacitance between said circuit node and said first voltage reference;
• alternately connecting a second end of said first capacitor, through a second switch circuit, to an amplifier input and a second voltage reference;
• and
• adding a second capacitor between said circuit node and said first voltage reference to compensate for the non-linear effects of the switched capacitor circuit, said second capacitor being selected to have a capacitance greater than said parasitic capacitance and an impedance lower than a conduction resistance of said first and second switch circuits at the predetermined frequency.