A digitally programmable switched-capacitor universal active filter/oscillator

A universal second-order switched-capacitor filter section has been fabricated on an NMOS chip. The device can perform all five basic filter types as well as a sine wave oscillator without external components, while requiring only an external clock. The filter type is determined by selecting one or more of three input pins. The filter response is determined by ten external programming pins which may be either digitally controlled or hard wired.