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Schmitt trigger circuit using MOS transistors and having constant threshold voltages

  • US 4,563,594 A
  • Filed: 07/25/1983
  • Issued: 01/07/1986
  • Est. Priority Date: 07/30/1982
  • Status: Expired due to Term
First Claim
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1. A Schmitt trigger circuit having lower and higher threshold voltages, comprising:

  • first and second power supply terminals between which an operating voltage is applied;

    first MOS inverter means including a complementary channel conductivity pair of first and second MOS transistors each having a drain, a source and a gate, said first and second MOS transistors having their gates connected together to receive an input voltage signal, and their sources connected to said first and second power supply terminals, respectively, and circuit means connected between the drains of said first and second MOS transistors for transmitting a potential variation at the drain of one of said first and second MOS transistors, which potential variation is caused by a voltage variation of said input voltage signal, to the drain of the other transistor after a delay;

    second MOS inverter means responsive to said first MOS inverter means; and

    feedback circuit means responsive to said second MOS inverter for suppressing the potential variation at the drain of at least one of said first and second MOS transistors of said first MOS inverter means until said input voltage signal becomes lower than said lower threshold voltage or higher than said higher threshold voltage of said Schmitt trigger circuit; and

    output means coupled to said feedback circuit means for providing an output voltage signal of said Schmitt trigger circuit.

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