Protection circuit for MOS driver

Claim 2

In combination: an MOS device having gate, source and drain electrodes operative when energized to supply an output voltage signal at said drain electrode in response to a received input voltage signal at said gate electrode; static charge storage means connected to said Drain electrode; capacitance means; switching means for selectively connecting said capacitance means to said gate electrode of said MOS device so as to minimize voltage feedback across the drain to gate junction of said MOS device when the device is energized and to isolate said capacitance means from said gate electrode so as to increase voltage feedback across the drain to gate junction of said MOS device in order to protect said MOS device from spurious voltage signals resulting from said static charges applied to said drain electrode when said MOS device is deenergized; and means for supplying a control voltage to said switching means to control the operation thereof.

Claim 3

The combination of claim 1, wherein said output voltage signal at said drain electrode is mutually different from said input voltage signal received at said gate electrode when said MOS device is energized.

Claim 4

A driver circuit having input and output terminals and subject to the application of spurious voltage signals at said output terminal resulting from static charge and the like comprising: a driver insulated-gate field effect transistor having a gate electrode connected to said input terminal, a drain electrode connected to said output terminal, and a source electrode connected to a reference voltage source; said driver transistor having a source-drain conduction path controlled by input voltage signals at said gate electrode for establishing output voltage signals at said drain electrode, said driver transistor further having capacitance connected between said drain and gate electrodes which is operative to feed back to said gate electrode a fraction of the voltage signal at said drain electrode; capacitance means for connection to said reference voltage source and to said gate electrode for reducing the fraction of said output voltage signal fed back to said gate electrode; switching means connected to said last mentioned capacitance means and to said gate electrode for selectively connecting said capacitance means to said gate electrode; and means for controlling said switching means for isolating said capacitance means from said gate electrode when said driver circuit is de-energized in order to increase the fraction of output voltage fed back to said gate electrode, whereby an increased fraction of any spurious voltage signal at said drain electrode from static charge or the like is coupled to said gate electrode for more rapidly rendering said transistor conductive to discharge said spurious voltage signal therethrough along said source-drain conduction path to said reference voltage source.

Claim 5

A driver circuit having input and output terminals and subject to the application of spurious voltage signals at said output terminal resulting from static charge and the like comprising: a driver insulated-gate field effect transistor having a gate electrode connected to said input terminal, a drain electrode connected to said output terminal, and a source electrode connected to a reference voltage source; said driver transistor having a source-drain conduction path controlled by input voltage signals at said gate electrode for establishing output voltage signals at said drain electrode, said driver transistor further having capacitance connected between said drain and gate electrodes which is operative to feed back to said gate electrode a fraction of the voltage signal at said drain electrode; capacitance means for connection to said reference voltage source and to said gate electrode for reducing the fraction of said output voltage signal fed back to said gate electrode; switching means connected to said last mentioned capacitance means and to said gate electrode for selectively connecting said capacitance means to said gate electrode; and means for controlling said switching means for isolating said capacitance means from said gate electrode when said driver circuit is de-energized in order to increase the fraction of output voltage fed back to said gate electrode, whereby an increased fraction of any spurious voltage signal at said drain electrode from static charge or the like is coupled to said gate electrode for more rapidly rendering said transistor conductive to discharge said spurious voltage signal therethrough along said source-drain conduction path to said reference voltage source.

Claim 6

The driver circuit of claim 3 wherein said switching means is a switching insulated gate field effect transistor having the source-drain path thereof connected between said capacitance means and said gate electrode of said driver transistor.

Claim 7

The driver circuit of claim 4 wherein said wherein said switching transistor has a gate electrode connected to receive a fixed voltage level for rendering said switching transistor conductive while said driver circuit is energized.

Claim 8

The driver circuit of claim 4 wherein said driver insulated-gate field effect transistor and said switching insulated gate field effect transistor are each of the same conductivity type.

Claim 9

The driver circuit of claim 3, including source means connected to said input terminal through input switching means in order to selectively supply the gate electrode of said driver transistor with an input voltage signal to thereby control the operation of said driver transistor.

Claim 10

The driver circuit of claim 7 wherein said input switching means is a field effect transistor having source, gate and drain electrodes, said source and drain electrodes forming a conduction path therebetween to electrically connect said last mentioned source means to the gate electrode of the driver transistor through said input terminal when said input switching means is rendered cOnductive, said driver transistor gate electrode isolated from said last mentioned source means when said input switching means is rendered non-conducting whereby said driver transistor gate electrode electrically floats at the voltage of said input signal.