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Pulse width modulator circuit for switching regulators

  • US 4,743,783 A
  • Filed: 08/25/1986
  • Issued: 05/10/1988
  • Est. Priority Date: 01/16/1984
  • Status: Expired due to Term
First Claim
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1. A circuit for signal summing useful in pulse width modulators, said circuit comprising:

  • first and second power supply terminals connectable to a source of operating power;

    a first transistor having a base coupled to a first signal voltage source, an emitter coupled to one terminal of a first scaling and linearizing resistor, and a collector coupled to one terminal of a first load element;

    a second transistor having a base coupled to a second voltage signal source, an emitter coupled to one terminal of a second scaling and linearizing resistor, and a collector coupled to one terminal of a second load element;

    means for coupling the other terminals of said first and second load elements to said first power supply terminal;

    means for coupling the other terminals of said first and second scaling and linearizing resistors respectively through first and second constant current devices to said second power supply terminal;

    a third transistor having a collector coupled to said collector of said first transistor, an emitter coupled to one terminal of a third scaling and linearizing resistor, and a base coupled to a third voltage signal source;

    a fourth transistor having a collector coupled to said collector of said second transistor, an emitter coupled to one terminal of a fourth scaling and linearizing resistor, and a base coupled to a fourth voltage signal source;

    means for coupling the other terminals of said third and fourth scaling and linearizing resistors respectively through third and fourth constant current devices to said second power supply terminal whereby said first and third voltage signal sources are summed in said first load element and said second and fourth voltage signal sources are summed in said second load element.

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