Linear power amplifier bias circuit
First Claim
1. A bias circuit for biasing a transistor power amplifier, said bias circuit comprising:
- a first transistor comprising a base, a collector, and an emitter, said base of said first transistor coupled to a base of an associated amplifier transistor and a first end of an input signal coupling capacitor, and said emitter coupled to a signal ground node common with an emitter of the associated amplifier transistor;
a second transistor comprising a base, a collector, and an emitter, said base of said second transistor coupled to said collector of said first transistor, and said collector of said second transistor coupled to an operating voltage signal; and
a first impedance element having a first end coupled to said collector of said first transistor and said base of said second transistor and a second end coupled to a reference voltage signal;
wherein said bias circuit is operative to provide a bias current responsive to an amplitude of the radio frequency signal to be amplified with a current gain capable of being configured to be greater than unity.
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Accused Products
Abstract
A bias circuit suitable for use with a radio frequency linear power amplifier compensates for amplifier gain compression by providing bias current responsive to an amplitude of an RF signal to be amplified at a bias current gain greater than unity. The bias circuit comprises a minimal number of active and passive components and is suitable for implementation in a range of process technologies. Bias current gain may be configured over a range of less than to greater than unity gain by adjusting a reference voltage supplied to the bias circuit and by adjusting a resistor value included within the bias circuit. In implementation, the bias circuit is configured to have a bias current gain that complements a characteristic gain compression associated with a particular radio frequency power amplifier.
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Citations
41 Claims
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1. A bias circuit for biasing a transistor power amplifier, said bias circuit comprising:
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a first transistor comprising a base, a collector, and an emitter, said base of said first transistor coupled to a base of an associated amplifier transistor and a first end of an input signal coupling capacitor, and said emitter coupled to a signal ground node common with an emitter of the associated amplifier transistor;
a second transistor comprising a base, a collector, and an emitter, said base of said second transistor coupled to said collector of said first transistor, and said collector of said second transistor coupled to an operating voltage signal; and
a first impedance element having a first end coupled to said collector of said first transistor and said base of said second transistor and a second end coupled to a reference voltage signal;
wherein said bias circuit is operative to provide a bias current responsive to an amplitude of the radio frequency signal to be amplified with a current gain capable of being configured to be greater than unity. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A bias circuit for biasing a radio frequency amplifier, said bias circuit comprising:
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a first transistor driven by a radio frequency signal to be amplified by the radio frequency amplifier and adapted to output a bias control signal responsive to the radio frequency signal to be amplified; and
a second transistor driven by said bias control signal and adapted to provide a bias current to the radio frequency amplifier responsive to said bias control signal;
wherein said bias circuit provides said bias current to the radio frequency amplifier proportional to an amplitude of the radio frequency signal to be amplified. - View Dependent Claims (21, 22, 23)
a first impedance element coupled between a bias voltage supply and said first transistor; and
a second impedance element coupled between said second transistor and the radio frequency power amplifier;
wherein a current gain of said bias current may be adjusted to a desired value based on setting values for said first and second impedance elements.
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22. The bias circuit of claim 20 wherein said second transistor derives said bias current from an operating voltage supply.
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23. The bias circuit of claim 20 wherein said second transistor derives said bias current from an output of the radio frequency amplifier.
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24. A radio frequency power amplifier circuit comprising:
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a first transistor having a base, a collector, and an emitter, said emitter of said first transistor coupled to a signal ground node;
a second transistor having a base, a collector, and an emitter, said collector of said second transistor coupled to a voltage source, and said base of said second transistor coupled to said collector of said first transistor;
a third transistor having a base, a collector, and an emitter, said emitter of said third transistor coupled to said signal ground node and said base of said third transistor coupled to said base of said first transistor, said collector of said third transistor providing an amplified output signal;
a first impedance element having a first end coupled to said collector of said first transistor and said base of said second transistor and a second end coupled to a reference voltage signal; and
a first capacitor having a first end coupled to a radio frequency signal to be amplified and a second end coupled to said bases of said first and third transistors;
wherein said first and second transistors and said first impedance element cooperate to form a bias circuit providing a bias current proportional to an amplitude of the radio frequency signal received through said first capacitor to be amplified by said third transistor. - View Dependent Claims (25, 26, 27, 28, 29, 30, 31, 32, 33)
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34. An integrated circuit device comprising:
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a reference voltage node adapted to receive a reference voltage signal;
an operating voltage node adapted to receive an operating voltage signal;
an output signal node adapted to provide an output RF signal;
an input signal node adapted to receive a radio frequency signal to be amplified;
a plurality of coupling capacitors having first ends commonly connected to said input signal node;
a plurality of parallel amplifier transistors, each having a base, an emitter, and a collector, wherein respective ones of said bases are connected to respective ones of second ends of said coupling capacitors, all said emitters are commonly connected to a signal ground node and all said collectors are commonly connected to said output signal node; and
a plurality of bias circuits wherein respective ones of said bias circuits are connected to respective ones of said parallel amplifier transistors and adapted to provide a bias current that operates said parallel amplifier transistors in a substantially linear mode of operation over a range of amplitudes of the radio frequency signal to be amplified, each said bias circuit comprising;
(i) a first transistor comprising a base, a collector, and an emitter, said base coupled to said base of a respective one of said amplifier transistors and said second end of a respective one of said coupling capacitors, and said emitter coupled to said signal ground node;
(ii) a second transistor comprising a base, a collector, and an emitter, said base coupled to said collector of said first transistor, and said collector coupled to said operating voltage node; and
(iii) a first impedance element having a first end coupled to said collector of said first transistor and said base of said second transistor and a second end coupled to said reference voltage node. - View Dependent Claims (35, 36, 37, 38, 39)
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40. A bias circuit for biasing a transistor power amplifier, said bias circuit comprising:
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a first transistor circuit for generating an analog control signal responsive to an amplitude of a radio frequency signal to be amplified by the transistor power amplifier; and
a second transistor circuit for generating a bias current responsive to said analog control signal;
wherein said bias current maintains the transistor power amplifier in a linear mode of amplification across a range of amplitudes of the radio frequency signal to be amplified. - View Dependent Claims (41)
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Specification