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Preamplifier for optical communication having a gain control circuit

  • US 5,363,064 A
  • Filed: 04/22/1993
  • Issued: 11/08/1994
  • Est. Priority Date: 04/24/1992
  • Status: Expired due to Fees
First Claim
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1. A preamplifier for optical communication that amplifies an input signal produced by a photodetector, comprising:

  • a phase-inverting amplifier including an input-state FET and a load thereof, for amplifying the input signal;

    gain control means for increasing a bandwidth for the preamplifier so that the preamplifier bandwidth remains wider than a bandwidth of an optical receiver which includes the preamplifier, the increase being achieved by reducing an effective load resistance to lower an open-loop gain of the phase-inverting amplifier when a current flowing through the load exceeds a first predetermined value;

    a feedback resistor provided in a negative feedback path of the phase-inverting amplifier; and

    bypass means for reducing an effective feedback resistance when a feedback quantity exceeds a second predetermined value.

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