Appeal No. 1999-1640
Application 08/782,464
appeal. Figure 2B is exclusively relied upon by the examiner in Brannon as a basis for the
claimed cascoded switching elements or transistors of the claims on appeal.
We are unpersuaded by the examiner’s stated reasoning of Brannon based upon
the indication at column 4, lines 45 through 48, and perhaps better stated at column 5,
lines 13 through 16, that the use of cascoded transistors reduces the input capacitance of
the transistor Q1 in Figure 2 of Brannon over that circuit provided in Brannon’s prior art
Figure 1 as a basis for combinability with appellants’ admitted prior art Figures 1 and 2.
There is no stated problem with the input capacitance associated with appellants’ prior art
Figures 1 and 2 in the discussion of them in the specification as filed.
Moreover, appellants’ position at the top of page 7 of the brief that Brannon is
directed to a read differential preamplifier which does not include switching elements for
switching a load is a compelling argument against obviousness. Each of the claims on
appeal requires that the stated switches in the claims actually switch the load also recited
in each claim. A read preamplifier as in Brannon forms no such switching function but only
outputs a preamplified differential input for subsequent, further amplification. Thus, the
artisan would not necessarily have even looked to such preamplifier circuits as in Brannon
for teachings to overcome the stated disadvantages of the appellants’ admitted prior art
Figures 1 and 2 write drivers anyway. We are therefore left with the conclusion that the
examiner’s basis of the rejection derives from prohibited hindsight based upon appellants’
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