Appeal No. 1997-2297 Page 8
Application No. 08/337,636
Schmitt trigger 13, Schmitt trigger 13 device sizing, and the
unusual sizing of NMOS transistor 31 so that it is from five
to fifteen times larger than the gate sizes of the pull-up
driver 15." Thus, we find that NMOS transistor helps provide
noise filtering and is not just a mere "change in size." We
observe that Koker (figure 5) resorts to the use of additional
inverter circuits to protect against glitches in the input
circuit, and that the examiner is correct (answer, page 10) to
the extent that in general, adjusting the relative sizes of
transistors is known to those of ordinary skill in the art.
However, we find no suggestion in Koker, who teaches that the
gate width of the inverter is the same 6 microns as the gate
width of the first gate P1pa, to configure the inverter
(buffer) such that the inverter has a first input gate size of
a pull-down device that is at least five times greater than
the first gate size of the Schmitt trigger, as recited in
claim 1. In our view, the only suggestion for modifying Koker
in the manner proposed by the examiner to meet the above-noted
limitation stems from hindsight knowledge derived from the
appellants' own disclosure. The use of such hindsight
knowledge to support an obviousness rejection under 35 U.S.C.
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