This dissertation proposes implementation of high performance filters using integrators. In the first-half part discussion is focused on improvement of filter characteristics by deriving novel filter structures. First, sensitivities of group-delay characteristics with respect to unity-gain frequencies of integrators are considered. The sensitivities of all-pole low-pass filters are analyzed and structures of filters with low sensitivities are proposed. Second, structures of filters with minimum equivalent input noise spectral density at DC are proposed. For all-pole low-pass filters simple structures are derived after all noise sources are modeled as equivalent input noise of integrators. Third, filter design considering effect of parasitic elements is described. The consideration to relation between parasitic elements and filter structures concludes that a filter with small-spread element values will show good frequency characteristics regardless of parasitic elements. An algorithm finding out structures of filters with small-spread element values is also proposed.
In the last-half part several methods to reduce effect of parasitic elements are proposed for integrator-based filters including conventional approaches. First, selection from integrators with self feedback is discussed. A feedback from the output terminal of an ideal integrator to its input terminal is equivalent to addition of a resistor to itself as a load. Filter frequency characteristics are affected by nonidealities of actual integrators. An appropriate selection method is proposed and it is confirmed that the method improves filter characteristics. Second, interference of input and output impedances is considered. Effect of the interference at low frequencies can be driven into frequency shift, which is automatically tuned on an integrated circuit, by modifying an integrator-based filter with appropriate addition of dummy building blocks i.e. unity-gain buffers. Third, predistortion of filter transfer functions is presented. The predistortion requires integrators with electrically controllable unity-gain frequencies, the same structure, and the same element values. This restriction on integrators makes the predistortion quite easy. Last, the predistortion is applied to an automatic tuning system. A circuit which detects parameters required in the predistortion is proposed. The detected parameters change only unity-gain frequencies of integrators to control frequency characteristics of a signal processing filter and adjust frequency characteristics appropriately.