Hameg Instruments HZ530 Manual Del Usuario página 40

R combination in surface mount technology (SMT). Some offered
three-pole capacitors are poor high frequency filters.
Another example is a wideband choke used as a signal line filter.
Figure 6 shows the results. The frequency spectrum is poorly
suppressed, but the risetimes are significantly slowed down. It
should be noticed here that a time domain analysis only will lead
to poor EMC performance and the wrong conclusions. This is an
expensive measure that will influence the digital function with
disappointing EMC suppression.
As a final example a modern SMT chip filter consisting of two ferrite
beads and a feed-through capacitor is shown.
Figure 7 shows the results which are relatively good. The spec-
trum is limited and the risetime is surprisingly fast. The over- and
under-shoot is somewhat disappointing. This occurs in filters which
consist of only inductance and capacitance.
In conclusion, it is observed that the digital circuit designer who is
aware of EMC problems, must look at the frequency domain and
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