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Amplifying circuit with adjustable amplification and transmitter system comprising such an amplifying circuit

  • US 20050174175A1
  • Filed: 01/10/2005
  • Published: 08/11/2005
  • Est. Priority Date: 07/10/2002
  • Status: Active Grant
First Claim
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1. An amplifier circuit with adjustable gain, comprising:

  • an input terminal pair configured to receive a differential input signal;

    an output configured to output an amplified version of the differential input signal;

    a control input configured to supply a gain factor to the amplifier circuit;

    a cascode stage connected to the output and comprising two cascode transistors coupled together at a control terminal thereof;

    a plurality of differential amplifiers connected together in parallel, each comprising a respective differential input connected to the input terminal pair, a respective differential output connected to the cascode stage, and a respective activation input, and wherein each differential amplifier further comprises two differential amplifier transistors coupled to a current mirror transistor, and wherein the current mirror transistor is coupled to the activation input and, together with the differential amplifier transistors, is configured to supply a reference current based on a signal at the activation input; and

    an actuation unit comprising an input connected to the control input of the amplifier circuit, and a plurality of outputs, a respective one of which is connected to the activation input of a respective differential amplifier, and configured to selectively activate one or more differential amplifiers based on the gain factor supplied at the control input.

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