"Square root domain" filter design and performance

This paper discusses the implementation and performance of square root doma in filters, which can be considered as the CMOS equivalent of the bipolar l og domain technique. The square root design methodology is based on exploit ing the MOSFET large-signal square law characteristic to implement filters which are input-output linear, but operate with internally non-linear signa ls. The design of subcircuits required for the implementation of square roo t domain filters is described based on the MOSFET translinear principle, an d various performance issues are discussed. Simulation and measured results are also presented to confirm the validity of this approach, which may be attractive for low-voltage operation at frequencies in the MHz range.