Noise performance of state-space active filters

A novel approach to the noise analysis of state-space active networks is developed. The technique, when applied to the state-space active filters, results in a simple and elegant noise expression. The noise performances of the optimum normal bandpass section and of the Tow¿Thomas bandpass section are analysed. The results compare very well with previously published noise calculations using the conventional approach. Since the optimum normal biquads are not optimised in terms of noise performance, it is found that, in general, the optimum normal section is slightly noisier than the Tow¿Thomas section.