Abstract: A first switching circuit has an input for receiving a first input signal, and a second switching circuit has an input for receiving a second input signal. A node is connected to receive outputs from both the first and second switching circuits. A filter receives an unfiltered signal from the node to generate an output signal. A circuit is provided to alternately actuate the first and second switching circuits during a transition time period so as to smoothly transition the output of the filter between the first and second input signals. At least one of the first and second input signals is a time-varying analog signal. The smooth transition between the first and second input signals has a shape determined by pulse width and frequency characteristics of pulses output by the circuit to alternately actuate the first and second switching circuits. The shape may include a linear ramp, an S-shaped curve, a parabolic curve and a hyperbolic curve.