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Current comparator automatic output control

  • US 5,652,547 A
  • Filed: 09/11/1995
  • Issued: 07/29/1997
  • Est. Priority Date: 06/20/1995
  • Status: Expired due to Fees
First Claim
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1. A method for controlling an RF power amplifier output in an RF power amplifier comprising the steps of:

  • deriving a base bias current from a bipolar transistor having a base emitter voltage drop Vbe threshold voltage of a first magnitude and temperature variation;

    biasing a diode rectifier having a diode threshold voltage (Vd) of a second magnitude and temperature variation about the same as the first magnitude for providing a sensed current of an opposite polarity from said base bias current;

    summing said base bias current and said sensed current such that said first and second magnitude and temperature variations are canceled over temperature in a current node having an input, a first output connected to the base of said bipolar transistor, and a second output coupled to the anode of said diode rectifier;

    current comparing a level of sensed current, that is representative of the RF power amplifier current state of said RF power amplifier, with a reference current;

    providing said reference current for comparison with said sensed current and setting the RF power amplifier current state at said input of said current node; and

    providing an output that is coupled to said power amplifier so that the RF power amplifier current is maintained at an optimum level for minimizing temperature dependent variations and substantially leveling the power of said RF power amplifier.

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