Appeal No. 2000-1938
Application 08/940,467
The zener diodes ZD1 and ZD2 in the prior art power output stage
are provided to limit the voltage between drain Dr and gate G of
switching transistor T. Specification at 1, lines 13-15.
When the Zener protection cuts in, a pronounced kink is
produced in the time profile of the voltage. That may
result in an excessive emission of electromagnetic
radiation that can have a detrimental effect on the
environment. That is to say other electrical or
electronic systems, in automobiles, for example[] a car
radio[,] may be detrimentally affected by the
electromagnetic radiation emission.
Id. at 1, 11. 15-22.
Figure 3, reproduced below, shows how drain voltage UDr
varies in response to control signal Ust in the circuits of
Figures 1 and 2, the only difference occurring at time t3, which
shows the above-noted kink or sharp transition in the drain
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