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Floating current source

  • US 4,990,845 A
  • Filed: 12/18/1989
  • Issued: 02/05/1991
  • Est. Priority Date: 12/18/1989
  • Status: Expired due to Term
First Claim
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1. A floating current source, comprising:

  • two field effect transistors FET'"'"'s, one of said FETs defining a reference FET (FET-R) and the other defining a floating output FET, FET-O;

    FET-R having its gate connected to a reference voltage VR, and its source connected to receive an input current from an input current source and to generate a gate-to-source voltage which when applied as a gate-to-source voltage to FET-O will generate an output current in FET-O equal to the input current or a multiple thereof; and

    circuit means for applying source of FET-O a voltage equal to the gate-to-source voltage of FET-R, including a series circuit having two matching resistors, R1 and R2, means for generating a voltage V1 across R1 substantially equal to the gate-to-source voltage at FET-R, means for generating a substantially equal voltage V2 across R2, and means for applying V2 across the gate and source of FET-O.

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