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A general and efficient CAD method for simulation of switched capacitor filters and A/D and D/A converters, is demonstrated. It is based on the direct implementation of controlled switch branches into the widely used modified nodal analysis technique and is therefore in contrast to other methods, directly compatible with existing CAD techniques. It allows for DC, time domain, and frequency response calculations for arbitrary clock cycles and all types of inputs (piecewise constant, sample and hold, and continuous). The circuit can also contain resistors and allows for nonlinear time domain analysis too. As implemented in the Diana program it allows for full top-down design from principle to transistor level, including clock drivers, control logic, etc. Input is directly from the circuit diagram. The method is illustrated by practical design examples.