A new approach, to the exact analysis of linear circuits containing periodically operated switches is presented. After reformulation of the state equations conventional Fourier analysis is used to determine the response to arbitrary deterministic or stochastic inputs. The analysis is applicable also to improper circuits and circuits causing discontinuities in the state variables at the switching instants. The switches may operate in an arbitrary fashion with a common switching period. Explicit closed form solutions for both the (Fourier coefficients of the) periodically time-varying transfer function

and the impulse response

are derived. These results are most suitable for computer aided design. Applications to switched filters and modulators are given.