Integrated switched-capacitor FDNR filter

A switched-capacitor filter using a frequency-dependent negative resistance (FDNR) is described. FDNR filters closely simulate passive LC filters, thereby retaining passband stability and design simplicity. The filter has been implemented in LSI and designed to perform the transmit/receive filtering for PCM codecs. Circuits are described that overcome the floating node and floating amplifier problems previously associated with FDNRs.