Appeal No. 20005-1269
Application No.09/499,060
turns to Figure 4 of Tanigawa for a disclosure of a specific current sink comprising a
current generator 9 having a first resistance (the internal resistance of current source 9)
and a circuit (Q1, Q2, R) having a second resistance. The examiner asserts that
Tanigawa discloses the advantage of gain control and that it is “notoriously well known
that to modify a current sink circuit...to a current source circuit, such requires changing
the conductivity types of the transistors and the polarities of the power supply” (answer-
page 4). The examiner specifically points to Figures 8 and 9 of Lauffenburger to show
the “notoriety of this modification” (answer-page 4).
The examiner then concludes that it would have been obvious to modify the
Figure 4 circuit of Tanigawa to be a current source circuit by changing the conductivity
types of transistors Q1 and Q2 and the polarities of the power supply, as suggested by
Lauffenburger. Further, contends the examiner, it would have been obvious to use the
specific current source of Tanigawa, as modified, for the broad current source Ig1 of
APA for the expected advantage of obtaining a constant current with gain control (see
page 4 of the answer).
The examiner further contends that it would have been obvious to provide the
combination of APA, Tanigawa and Lauffenburger “in integrated form to obtain the
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