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Low voltage CMOS circuit for on/off chip drive at high voltage

  • US 6,031,394 A
  • Filed: 01/08/1998
  • Issued: 02/29/2000
  • Est. Priority Date: 01/08/1998
  • Status: Expired due to Term
First Claim
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1. A low voltage and low current CMOS circuit for providing a high voltage output while protecting the CMOS devices from various breakdown mechanisms, comprising:

  • a) a first CMOS cascode chain including PMOS and NMOS devices;

    b) a second CMOS cascode chain including PMOS and NMOS devices and connected in cascade with the first CMOS cascode chain;

    c) means cross coupling the PMOS devices in the first and second cascode chains;

    d) means cross coupling the NMOS devices in the first and second cascode chains;

    e) a third CMOS cascode chain including PMOS and NMOS devices, the PMOS devices coupled to the cross coupled PMOS and the NMOS devices coupled to the cross coupled NMOS devices for buffering the PMOS devices in the first and second cascode chains;

    f) high and low voltage power rails connected to the first, second and third CMOS cascode chains;

    g) an input circuit connected to the first and second CMOS cascode chains and providing low voltage input signal levels;

    h) means coupling the gates of the first, second and third CMOS cascode chains to bias supplies for limiting current flow in the first, second and third cascode chainsi) a CMOS cascode output circuit including PMOS and NMOS devices and connected between the high and low voltage power rails and to the third CMOS cascode chain, the output circuit providing a high voltage or low voltage output according to the input signal level;

    j) a clamping circuit connected to the PMOS output devices for limiting the maximum voltage across the PMOS output devices; and

    k) means dynamically changing the bias levels of the PMOS and NMOS devices in the first, second, third cascode chains and the output circuit whereby such PMOS and NMOS devices do not exceed their breakdown voltages as the output circuit provides a high or low voltage output.

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