Canonical design of integrated ladder filters

Necessary conditions are given for the existence of a one-opamp-per-pole (canonical) realisation of a transfer function by an active ladder filter designed by operational simulation methods. The parity of the transfer function is shown to be critical. Some new design methods are applied to guarantee canonical low-sensitivity realisation of hitherto problematic filter types. These ensure a uniform progression of circuit structures with filter order. Hybrid matrix methods are shown to be useful to minimise the use of opamps in the simulation of arbitrary prototype ladder topologies.