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Linear differential amplifier

  • US RE36,861 E
  • Filed: 03/08/1999
  • Issued: 09/12/2000
  • Est. Priority Date: 10/12/1987
  • Status: Expired due to Term
First Claim
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1. A linear differential amplifier, comprising:

  • a pair of first and second transistors with their emitters coupled to each other;

    a pair of third and fourth transistors with their emitters coupled to each other, a collector of said first transistor being connected to a collector of said third transistor and a collector of said second transistor being connected to a collector of said fourth transistor;

    a pair of input terminals, one of which being coupled to a base of said first transistor, the other one of which being coupled to a base of said fourth transistor;

    a pair of output terminals, one of which being connected to said collectors of said first and said third transistor, the other one of which being connected to said collectors of said second and said fourth transistors;

    first voltage source means for applying first offset DC voltage between one of said input terminals and a base of said third transistor, said first voltage source means including a first pair of emitter-followers with each of said emitter-follower including transistors of same emitter areas but different collector currents, and first emitter current sources for each transistor of said first pair of emitter-followers which supply emitter currents corresponding to the collector currents;

    second voltage source means for applying second offset DC voltage of the same magnitude as said first offset DC voltage, between one of said input terminals and a base of said second transistor, said second voltage source means including a second pair of emitter-followers with each said emitter-follower including transistors of same emitter areas but different collector currents, and second emitter current sources for each transistor of said second pair of emitter-followers which supply emitter currents corresponding to the collector currents;

    constant current source means for supplying emitter currents to said first, second, third, and fourth transistors; and

    load resistor means for converting collector currents of said first, second, third, and fourth transistors into output voltages.

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