A novel fully programmable switched-current IIR filter

A fully programmable switched-current IIR filter using switched-current delay-multiplies units is described. The characteristics of the filter are fully programmable by simply changing the ratios of the coefficient transistors. To reduce the effect of non-ideal characteristics of MOS transistors, a high-performance differential switched-current memory cell is used as a basic building block. To reduce the chip area and maintain the required accuracy of the coefficients, an array consisting of three different sizes of transistors is designed instead of using a unit transistor array as coefficient transistors. A prototype second-order switched-current IIR filter array which consists of six second-order switched-current IIR filters has been fabricated with the standard 1.2 /spl mu/m CMOS process technology. Hard wiring technique is used for programming the filters. The test results show that the characteristics of the filters satisfy the design requirements.