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SEMICONDUCTOR DEVICE

  • US 3,819,952 A
  • Filed: 01/29/1973
  • Issued: 06/25/1974
  • Est. Priority Date: 01/29/1973
  • Status: Expired due to Term
First Claim
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1. A semiconductor device, comprising:

  • an insulated gate field effect transistor to be protected against overvoltages including a first gate electrode, a first source electrode and a first drain electrode;

    an input terminal;

    a resistor connected to said input terminal and to said first gate electrode of said protected, insulated gate field effect transistor;

    a first protecting insulated gate field effect transistor having a threshold voltage level and including a second drain electrode connected to said first gate electrode of said protected transistor a second source electrode connected to said first source electrode of said protected, insulated gate field effect transistor, and a second gate electrode;

    a second protecting, insulated gate field effect transistor having a second threshold voltage level higher than the threshold voltage level of said first protecting, insulated gate field effect transistor; and

    means for electrically connecting said second protecting insulated gate field effect transistor to both said input terminal and said first protecting, insulated gate field effect transistor, said second, protecting, insulated gate field effect transistor having a third source electrode connected to said second gate electrode of said first protecting, insulated field effect transistor and being responsive to a voltage applied to said input terminal in excess of the second threshold voltage level to thus conduct and provide an output voltage and said first protecting, insulated gate field effect transistor being responsive to said output voltage from said second protecting, insulated gate field effect transistor and being conductive, thus applying a reduced voltage to said first gate electrode of said protected, insulated gate field effect transistor.

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