Application No. 08/176,867
nor any of the other references, shows or suggests any current
comparisons as required by the third element of claim 1. With
respect to Figure 1 of Clapper, it is urged that three inputs A, B
and C drive emitter followers 16, 26 and 30 which, in turn, bias
current sources 32, 36 and 39 having common collectors. The
collector currents generated in response to the A, B and C inputs
are coupled to a –15 volt reference through resistor 34, and are
thereby converted to a voltage at node E which is proportional to
the sum of the three collector currents. This voltage level is
then compared to three thresholded outputs which have different
threshold voltages, and thereby produce the sum and carry voltage
signals. Figure 3 shows the four possible voltage levels on node
E and the resultant sum and carry outputs. This is a voltage
level operation and only voltage comparisons are performed in the
outputs. Because there is no teaching of current comparison, as
in claim 1 and all of the other claims on appeal, it is urged that
the claims are patentable over the prior art.
The examiner admits that Basehore does not disclose
current adders and comparators, and that instead Basehore utilizes
digital computation. It is urged that Clapper discloses an adder
which uses current generators and transistors to represent a
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