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Constant current circuit

  • US 7,474,145 B2
  • Filed: 02/08/2007
  • Issued: 01/06/2009
  • Est. Priority Date: 02/09/2006
  • Status: Expired due to Fees
First Claim
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1. A constant current circuit, comprising:

  • first and second depression type MOS transistors having drains connected to a high electric potential side; and

    first, second, and third enhancement type MOS transistors having sources connected to a low electric potential side;

    wherein a source of the first depression type MOS transistor and a drain of the first enhancement type MOS transistor are connected so that a first connection is formed,a gate of the first depression type MOS transistor and a gate of the first enhancement type MOS transistor are connected so that a second connection is formed;

    the second connection and the first connection are connected so that a third connection is formed;

    a source of the second depression type MOS transistor and a drain of the second enhancement type MOS transistor are connected via a resistance so that a fourth connection is formed;

    a gate of the second depression type MOS transistor and a gate of the second enhancement type MOS transistor are connected so that a fifth connection is formed;

    the fifth connection and the first connection are connected so that a sixth connection is formed;

    a gate of the third enhancement type MOS transistor is connected to the fourth connection between the drain of the second enhanced type MOS transistor and the resistance so that a seventh connection is formed; and

    a drain of the third enhancement type MOS transistor is an output end of the constant current circuit.

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