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Warning device

  • US 4,138,664 A
  • Filed: 12/14/1976
  • Issued: 02/06/1979
  • Est. Priority Date: 12/14/1976
  • Status: Expired due to Term
First Claim
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1. An improved warning device comprising means for detecting the presence of predetermined phenomena and for generating a first signal which changes to a predetermined value upon the presence of said phenomena in predetermined concentrations;

  • indicator means having an active and an inactive state;

    integrated circuit means formed on a single substrate and connected with said detecting means and said indicator means and responsive to said detecting means to place said indicating means in said active state, said integrated circuit means including means for generating a reference potential, a differential amplifier including first and second field-effect transistors (FETs), said first FET connected at a gate electrode thereof directly with said detecting means for receiving said first signal, said second FET connected at a gate electrode thereof with said reference potential, said first FET connected with said second FET to control the conductivity between drain and source electrodes thereof in accordance with the value of said first signal, said drain-source circuit of said second FET providing a second signal, and second circuit means including a third FET connected at a gate electrode thereof with said drain-source circuit of said second FET for having the conductivity between drain and source electrodes thereof controlled by the conductivity of said second FET, and impedance means connected in series circuit with the drain-source circuit of said third FET for developing a third signal thereacross, said third signal having a value in accordance with the conductivity of said third FET; and

    switch means connected with said impedance means and said indicator means for having said third signal applied thereto, said switch means being responsive to said third signal to place said indicator means in said active state.

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