Appeal No. 1996-4118
Application 08/ 084,255
The invention relates to arrangements for protecting electrical circuits from overcurrents. In
particular on page 9 of the specification, Appellants disclose that figure 3 shows a two terminal
protection arrangement in which an enhancement mode MOSFET 1 passes the operating current of the
circuit. The gate of the switching transistor 1 is connected to its drain via a battery 3 and a current
limiting resistor 5. A control MOSFET 4 is connected across the gate-source junction of transistor 1.
The gate voltage of the control transistor 4 is held by a voltage divider formed from resistance 6 and
resistance 7 which span the switching transistor. In operation of this arrangement, the current required
to cause it to switch is determined by the potential divider resistors 6 and 7 in addition to the threshold
voltage of transistor 4 and the channel resistance of a switching transistor. On page 8 of the
specification, Appellants disclose that the arrangement must be disconnected from the circuit supply or
load so that it will reset itself.
Independent claim 1 is reproduced as follows:
1. A two terminal circuit protection arrangement which:
(1) is intended to be series connected in a line of a circuit to be protected;
(2) comprises:
(a) a series switching transistor which
i. is selected from bipolar transistors and field effect transistors and
(i) if it is a bipolar transistor, comprises a collector, an emitter and
2
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