Appeal No. 1998-0440
Application No. 08/351,578
F.2d 1044, 1052, 5 USPQ2d 1434, 1438 (Fed. Cir. 1988), cert.
denied, 488 U.S. 825 (1988). These showings by the examiner
are an essential part of complying with the burden of
presenting a prima facie case of obviousness. Note In re
Oetiker, 977 F.2d 1443, 1445, 24 USPQ2d 1443, 1444 (Fed. Cir.
1992). A mere assertion by the examiner that the pair of
transistors of Tanizawa could be driven by a differential
amplifier is no substitute for evidence as to why the skilled
artisan would have been led to use such a driver in the prior
art. Thus, we cannot sustain the rejection of claim 6 and its
dependents, claims 2 through 5, over Tanizawa.
Independent claims 8 and 13 do not recite the particular
driver stage, but instead specify that the n-channel
transistor is an n-channel power DMOS transistor. The
examiner admits (Answer, page 3) that Tanizawa fails to
disclose a DMOS transistor. Yet, he concludes (Answer, page
4) that the substitution of a DMOS transistor for the n
channel MOS transistor of Tanizawa would have been obvious "as
a routine design expedient" as the replacement would be
"without any unexpected changes in the driver circuit's
operation." As pointed out by appellants (Brief, page 8) the
6
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