Noise performance of low-sensitivity active filters

Abstract

The noise limitations of some important low-sensitivity RC-active filter realizations are derived; the inherent rms noise (noise from essential network resistors) that exists at the output terminals of a bandpass active filter is determined for two-integrator loop and positive impedance converter filter realizations. Output noise spectral density and total rms output noise are determined for the two-integrator loop section. The noise contributed by the essential circuit resistors and the operational amplifiers is taken into account and it is shown that exact calculation of output noise may be obtained in terms of Q factor and impedance level. The results are used to obtain the theoretical noise limitations of these low-sensitivity active filters. It is found that the deterioration in signal-to-noise ratio (SNR), due to the internal filter noise, is independent of Q factor for high Q realizations.

Keywords

This publication has 16 references indexed in Scilit:

Inductorless bandpass filters
IEEE Journal of Solid-State Circuits, 1970
Two-port equivalent noise generators
Proceedings of the IEEE, 1970
Design formulas for active RC filters using operational-amplifier biquad
Electronics Letters, 1969
RC -active synthesis using positive-immittance convertors
Electronics Letters, 1967
Equivalent circuits of gyrators
Electronics Letters, 1967
Equivalent Gyrator Networks with Nullators and Norators
IEEE Transactions on Circuit Theory, 1967
The significance of nullators, norators and nullors in active-network theory
Radio and Electronic Engineer, 1967
Integratable gyrator using m.o.s. and bipolar transistors
Electronics Letters, 1966
Singular Network Elements
IEEE Transactions on Circuit Theory, 1964
Thermal Agitation of Electric Charge in Conductors
Physical Review B, 1928