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Constant current sources with programmable voltage source

  • US 5,154,172 A
  • Filed: 11/13/1989
  • Issued: 10/13/1992
  • Est. Priority Date: 11/13/1989
  • Status: Expired due to Term
First Claim
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1. A circuit for providing a constant current to a load, comprising:

  • a constant current source for connection to the load and having a control signal input for receiving a signal indicative of the desired current to be provided, said current source providing a constant current to the load when the voltage across said current source exceeds a predetermined value;

    a digitally programmable voltage source for coupling to the load and for coupling to said current source and having digital inputs and a voltage output, said voltage source providing the voltage impressed on said current source and the load, said voltage source providing an output level representative of an applied digital value provided to said digital inputs;

    means for monitoring the difference between the voltage across the load and the voltage supplied by said voltage source; and

    means coupled to said monitoring means and said voltage source digital inputs for changing said programmed value of said voltage source to increase said output voltage level when said difference is below a given level.

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