Electronic apparatus for biological research electronicappara00dona Year: 1958 INDUCTANCES, CAPACITANCES AND RESISTANCES The classical filter bears the same relationship to the R-C filter that the attenuator does to potential divider. That is, a classical filter is intended to work between a matched generator and load. Classical filters, like attenuators, are made up of sections which may be T or pi, and any number may be connected in cascade provided they are all designed for the correct character- istic resistance. The overall performance is then the sum of the several performances. T-sect
Electronic apparatus for biological research electronicappara00dona Year: 1958 INDUCTANCES, CAPACITANCES AND RESISTANCES The classical filter bears the same relationship to the R-C filter that the attenuator does to potential divider. That is, a classical filter is intended to work between a matched generator and load. Classical filters, like attenuators, are made up of sections which may be T or pi, and any number may be connected in cascade provided they are all designed for the correct character- istic resistance. The overall performance is then the sum of the several performances. T-section In Figure we see such a filter section in the T form, working between impedances Zq. For the present we work entirely in terms of impedance, in the interest of generality. The section comprises elements, as yet unspecified, of impedance Z-^jl in the series arms and Zg in the shunt arm. Figure The requirement for matching conditions to be fulfilled is that on removing one of the terminating impedances Zq and looking into the filter, we see an impedance Zq, that is â ^21 2 ' 0 Z2 + 2 I â¢^o whence If Zi and Z2 are pure reactances, and the bracketed term is positive, Zq is pure resistive, for both the product and the ratio ofy terms are real numbers. L/2 t L/2 Zo Figure Low-pass filter Value of elementsâIf the filter is to be low-pass we make Z^ an inductance L and Z^ a capacitance C {Figure ). Then jojL\ Z 2 â ^0 = (LVI-^
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