Current mirror biasing circuit with power control for HBT power amplifiers
First Claim
Patent Images
1. An electronic circuit comprising:
- a power amplifier having a radio frequency (“
RF”
) power transistor for amplifying radio frequency signals such that a quiescent DC collector current in the RF power transistor is approximately constant over an operational range of collector voltages supplied from a collector power supply;
a power amplifier bias transistor that biases the RF power transistor;
a current mirror bias transistor having an operating area such that the current mirror bias transistor has substantially a same current density as the power amplifier bias transistor when the current mirror bias transistor and the power amplifier bias transistor are biased from a reference voltage supply that supplies a reference voltage controlling an output power of the power amplifier and remains approximately constant as the collector voltage varies through the operational range;
a current mirror transistor biased by emitter current from the current mirror bias transistor and having an operating area such that a quiescent DC collector current density is about equal to a quiescent DC current density of the RF power transistor; and
a first base ballast resistor and a second base ballast resistor, the first base ballast resistor placed between an emitter of the current mirror bias transistor and a base of the current mirror transistor and having a resistance for a voltage drop that is about equal to a voltage drop across the second base ballast resistor placed between an emitter of the power amplifier bias transistor and a base of the RF power transistor.
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Abstract
An electronic circuit includes a current mirror bias circuit and a power amplifier that has a power transistor for amplifying radio frequency signals such that the output collector current of the power transistor is approximately constant over a wide range of varying power supply voltages. The power transistor is biased by a current mirror biasing circuit that has a reference voltage that maintains the quiescent DC collector current at an approximately constant value. The reference voltage may be varied to provide control of the output power of the power amplifier.
41 Citations
14 Claims
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1. An electronic circuit comprising:
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a power amplifier having a radio frequency (“
RF”
) power transistor for amplifying radio frequency signals such that a quiescent DC collector current in the RF power transistor is approximately constant over an operational range of collector voltages supplied from a collector power supply;a power amplifier bias transistor that biases the RF power transistor; a current mirror bias transistor having an operating area such that the current mirror bias transistor has substantially a same current density as the power amplifier bias transistor when the current mirror bias transistor and the power amplifier bias transistor are biased from a reference voltage supply that supplies a reference voltage controlling an output power of the power amplifier and remains approximately constant as the collector voltage varies through the operational range; a current mirror transistor biased by emitter current from the current mirror bias transistor and having an operating area such that a quiescent DC collector current density is about equal to a quiescent DC current density of the RF power transistor; and a first base ballast resistor and a second base ballast resistor, the first base ballast resistor placed between an emitter of the current mirror bias transistor and a base of the current mirror transistor and having a resistance for a voltage drop that is about equal to a voltage drop across the second base ballast resistor placed between an emitter of the power amplifier bias transistor and a base of the RF power transistor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9)
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10. An electronic circuit comprising:
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a power amplifier including a radio frequency (“
RF”
) power transistor for amplifying radio frequency signals such that a quiescent DC collector current of the RF power transistor is approximately constant over an operational range of supply voltage from a collector power supply;a power amplifier bias transistor that biases the RF power transistor; a current mirror transistor that mirrors the quiescent DC collector current in the RF power transistor; a current mirror bias transistor for establishing a reference current that flows as a collector current in the current mirror; and a first base ballast resistor and a second base ballast resistor, the first base ballast resistor placed between an emitter of the current mirror bias transistor and a base of the current mirror transistor and having a resistance for a voltage drop that is about equal to a voltage drop across the second base ballast resistor placed between an emitter of the power amplifier bias transistor and a base of the RF power transistor, wherein the current mirror bias transistor and the power amplifier bias transistor are adapted to be biased from a reference voltage sourced from a power supply supplying a set reference voltage within a control range of voltages, and the set reference voltage remains approximately constant over the operational range of the supply voltage from the collector power supply. - View Dependent Claims (11, 12)
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13. An electronic circuit comprising:
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a radio frequency (“
RF”
) power amplifier including at least one power transistor element for amplifying radio frequency signals at varying power levels such that a DC quiescent collector current for the RF power transistor is approximately constant over an operational range of collector voltages for a selected reference voltage;a power amplifier bias transistor for biasing the power transistor; a current mirror transistor that mirrors a DC quiescent collector current in the RF power transistor; a current mirror bias transistor for biasing the current mirror transistor, the current mirror bias transistor and the power amplifier bias transistor are adapted to be biased from a reference voltage sourced from a power supply separate from a power supply supplying the collector voltage for the RF power transistor, the reference supply voltage remaining about constant at the selected reference voltage over an operational range of collector; and a first base ballast resistor and a second base ballast resistor, the first base ballast resistor placed between an emitter of the current mirror bias transistor and a base of the current mirror transistor and having a resistance for a voltage drop that is about equal to a voltage drop across the second base ballast resistor placed between an emitter of the power amplifier bias transistor and a base of the RF power transistor. - View Dependent Claims (14)
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Specification