Appeal No. 2002-0397
Application 08/925,968
during the transition from a first to a second binary voltage
level (Br6). It is argued (Br6-7):
In other words, unlike a discrete resistor, the transistor
exhibits voltage "pumping" at the enable terminal to affect
the impedance between the input and output terminals during
a transition from the first to the second preselected
voltage level at the input terminal.
In fact, such "pumping" action is contrary to the
"attenuation" produced by an RC attenuator, in that the
effect of such pumping actually enhances signal propagation
from input to output terminals. Attenuation, by contrast,
involves the inhibition of signal propagation between
terminals.
It is argued that Nelson and the claimed invention are not
structurally the same because "the claimed circuit operates
differently (using charge pumping), with a different effect
(level shifting of a binary signal), using a different structure
(a biased transistor instead of a discrete resistor)" (Br8).
Appellant presents several additional arguments about the
different operation and different structure (Br9).
The examiner responds that "the resistor/capacitor parallel
combination of Nelson is an equivalent structure to appellant's
constantly biased FET/capacitor parallel combination . . . [t]wo
circuits that are structural equivalents can certainly be
considered to be structurally similar" (EA6).
Nelson discloses an RC attenuator comprising essentially a
voltage divider. Resistor R1 and capacitor C1 are connected in
parallel in a series path and resistor R2 and capacitor C2 are
connected in parallel in a shunt path (Fig. 3). The impedance of
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