Appeal No. 95-0648
Application 08/001,199
means for deactivating the discharge switching element when a signal applied to
the control terminal becomes zero or opposite in polarity from the drive signal
after the drive signal is reduced.
The examiner’s position in the supplemental examiner’s answer (Paper No. 19) is that this
limitation is met by Fig. 7 of Okado and that MOSFET 30 short circuits and deactivates the
switching element gate transistor 26 during a negative control signal. Reference is made by the
examiner to column 7, lines 45+, of Okado.
We disagree with this position. MOSFET 30 does not short circuit the gate of switching
element transistor 26 because of the large time constant exhibited by elements 28 and 29. At
column 7, lines 45-54, no reference is made to transistor 26, indicating that it is deactivated as
urged by the examiner. Contrary to the examiner’s position, at column 8, lines 26-35, Okado
teaches that the time constant of resistor 28 and diode 29 is large, such that the on time of
transistor 26 is longer than the oscillatory time of the voltage between the drain and source of the
BIFET transistor 1. This is the same type of operation as disclosed for appellants’ embodiment of
Fig. 5, wherein there is no deactivation of the discharge transistor 50. In that embodiment, diode
65 and resistor 66 correspond to aforementioned diode 29 and resistor 28, and the discharge
transistor 50 of Fig. 5 cannot be deactivated when a signal applied to the control terminal G
becomes zero or opposite in polarity because of the charge retained on the gate of transistor 50
due to the time constant of elements 65 and 66. It is only by the addition of a diode, such as
diode 42 in Fig. 9, that discharge transistor 50 can be deactivated when a signal applied to the
5
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