Synthesis of RC active filters with prescribed pole sensitivity

By using complex conjugate phantom zeros located in the left half of the p plane, a prescribed pole sensitivity is realised. The pole sensitivity thus achieved can be much less than that attainable by means of Horowitz´s or Herbst´s decomposition of the denominator polynomial of a given second-order low-pass transfer function. It is shown that two possible solutions for the co-ordinates of the phantom zeros exist depending on the directions along which the poles of the transfer function tend to migrate as a result of parameter variations. For the realisation of the phantom zeros two configurations are considered, one of which involves a voltage amplifier and the other involves a current amplifier. In both cases, shunt feedback is applied to the amplifier by means of an RC 2-port network which realises the complex conjugate phantom zeros. Two illustrative examples are included.