Appeal No. 1997-2297 Page 7
Application No. 08/337,636
claimed by applicant in the event the Schmitt trigger circuit
of Koker was driving other circuitry."
Appellants note (brief, page 7) that Koker does not show
the components that make up inverter INV1, but presumes the
inverter to comprise a pull-up device and a pull-down device.
Appellants argue that the applied prior art to Koker does not
suggest the claimed subject matter, asserting (id.) "that one
circuit with a Schmitt trigger and a buffer does not make all
other circuits with Schmitt triggers and buffers obvious,
since changes to relative gate sizes are not always obvious."
We agree.
Claim 1 requires that the buffer has a first input gate
size of a pull-down device that is at least five times greater
than the first gate size. We are not persuaded by the
examiner's assertion (answer, page 9) that "[o]bvious changes
in size are not patentable limitations" because we find no
teaching in the prior art to suggest that making the first
input gate size of a pull-down device in the buffer five times
greater than the first gate size would have been an obvious
change in size. Appellants disclose (specification, page 8)
that "noise filtering capability is due to the hysteresis of
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