VARIABLE DIRECT CURRENT BIAS CONTROL CIRCUIT FOR LINEAR OPERATION OF RADIO FREQUENCY POWER TRANSISTORS
First Claim
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1. A variable direct current bias control circuit for linear operation of radio frequency power transistors comprising:
- a radio frequency transistor amplifier having its base electrode coupled to an input circuit of radio frequency signals, its collector electrode coupled to a collector vOltage source and an output circuit, and its emitter electrode coupled to a common potential;
a biasing resistor coupled across the base electrode and emitter electrode of said radio frequency transistor amplifier to establish a gain factor for said amplifier;
a direct current transistor amplifier having said biasing resistor coupled across its emitter and base electrodes, the base electrode being coupled to a voltage divider circuit, and the collector electrode being coupled to said collector voltage source; and
a transistor having its emitter and collector electrodes coupled in series with the emitter and collector electrodes of said direct current transistor amplifier and its base biased from said collector voltage source to limit the current from said collector voltage source to said direct current transistor amplifier, whereby any attempted voltage drop across said biasing resistor resulting from increasing changes in radio frequency driving signal is compensated by increase in voltage across said biasing resistor by said direct current transistor amplifier to maintain the gain of said radio frequency transistor amplifier substantially constant.
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Abstract
A variable direct current (D.C.) bias control circuit for linear gain operation of a radio frequency (R.F.) power transistor having a DC amplifier coupled to sense the change in voltage drop across a biasing resistor of the RF power transistor and operative to maintain this voltage drop constant to provide a linear gain of the power transistor throughout 10 percent to 90 percent of its rated power output within a 1 1/2 decibel (db) variation.
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Citations
1 Claim
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1. A variable direct current bias control circuit for linear operation of radio frequency power transistors comprising:
- a radio frequency transistor amplifier having its base electrode coupled to an input circuit of radio frequency signals, its collector electrode coupled to a collector vOltage source and an output circuit, and its emitter electrode coupled to a common potential;
a biasing resistor coupled across the base electrode and emitter electrode of said radio frequency transistor amplifier to establish a gain factor for said amplifier;
a direct current transistor amplifier having said biasing resistor coupled across its emitter and base electrodes, the base electrode being coupled to a voltage divider circuit, and the collector electrode being coupled to said collector voltage source; and
a transistor having its emitter and collector electrodes coupled in series with the emitter and collector electrodes of said direct current transistor amplifier and its base biased from said collector voltage source to limit the current from said collector voltage source to said direct current transistor amplifier, whereby any attempted voltage drop across said biasing resistor resulting from increasing changes in radio frequency driving signal is compensated by increase in voltage across said biasing resistor by said direct current transistor amplifier to maintain the gain of said radio frequency transistor amplifier substantially constant.
- a radio frequency transistor amplifier having its base electrode coupled to an input circuit of radio frequency signals, its collector electrode coupled to a collector vOltage source and an output circuit, and its emitter electrode coupled to a common potential;
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Current AssigneeConstantine Kamnitsis, Robert Minton
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Original AssigneeConstantine Kamnitsis, Robert Minton
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InventorsMinton, Robert, Kamnitsis, Constantine
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Primary Examiner(s)Lake, Roy
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Assistant Examiner(s)Mullins, James B.
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Application NumberUS05/189,439Time in Patent Office474 DaysField of Search330/22,29,40US Class Current330/279CPC Class CodesH03G 3/3042 in modulators, frequency-ch...
