Appeal No. 1999-1855
Application 08/738,916
thrust of the non-enablement rejection appears to be that the
circuit of figure 4 cannot be made to work with a full range
of operation because if switch S11 were an "n-channel
transistor," it would have the same problems with respect to
parasitic diodes as disclosed when using an n-channel
transistor for S8 in figure 3.
Appellant does not respond to this rationale.
Nevertheless, we do not find the Examiner's reasoning
persuasive. The Examiner concludes, without analysis, that
switch S11 in figure 4 would have the same problem as switch
S8 in figure 3 if it were made using an n-channel transistor.
The specification discusses the problem with S8 as follows
(p. 3, lines 23-28, as amended):
[I]f switch S8 was made from an n-channel transistor 23
as shown in Figure 2, the N+ drain region 24 would be
connected to a negative voltage V , while the substrate
out
was connected to a higher voltage V . The parasitic
ss
diode 28b of the transistor will be forward biased, and
the output voltage V will be clamped to a maximum of one
out
diode voltage drop below V . [Emphasis added.]
ss
This situation does not apply to S11 in figure 4 because one
of the N+ regions would be connected to a positive voltage
2*V during the second cycle. Thus, the parasitic diode will
dd
be reverse biased and will not have the problem of switch S8.
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