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Improved Filter Disclosure Number: IPCOM000040039D
Original Publication Date: 1987-Sep-01
Included in the Prior Art Database: 2005-Feb-01

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Ett, AH [+details]


The classical filter used for suppression of unwanted line-conducted emissions is an L-section filter consisting of an inductor and capacitance. When used with low impedance digital circuits such as those used for peripheral interface, these circuits "ring" on line level transitions. This "ring" produces a damped oscillation with a peak- to-peak amplitude of twice the normal logic level, centered about the new logic level. This "ringing" provides signals below ground The first method described is the use of a silicon diode across the inductor in the circuit. The circuit of the classical filter is illustrated in Fig. 1, and the circuit for the modified circuit is illustrated in Fig. 2, along with the input and output waveforms.