Active protection circuit for load mismatched power amplifier
First Claim
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1. A method of protecting an amplifier, comprising the acts of:
- providing an amplifier including an input terminal adapted to receive a RF signal, an output terminal adapted to output the RF signal after amplification therein, and at least one amplifier stage between the input and output terminals;
providing a reference DC bias voltage to at least one said amplifier stage of the amplifier;
detecting an overpeak voltage output of the amplifier, wherein said detecting comprises using a series of diodes coupled to the output terminal of the amplifier; and
reducing the reference DC bias voltage in response to the detected overpeak voltage.
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Abstract
A peak detector detects an amplifier output overvoltage condition if the amplifier drives a mismatched load impedance. In response to the detected overvoltage condition, a clamping transistor lowers a reference DC bias voltage supplied by a bias circuit to the amplifier. The lowered reference DC bias voltage lowers amplifier gain and output power, thus protecting the amplifier.
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Citations
27 Claims
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1. A method of protecting an amplifier, comprising the acts of:
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providing an amplifier including an input terminal adapted to receive a RF signal, an output terminal adapted to output the RF signal after amplification therein, and at least one amplifier stage between the input and output terminals; providing a reference DC bias voltage to at least one said amplifier stage of the amplifier; detecting an overpeak voltage output of the amplifier, wherein said detecting comprises using a series of diodes coupled to the output terminal of the amplifier; and reducing the reference DC bias voltage in response to the detected overpeak voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of protecting an amplifier, comprising the acts of:
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providing an amplifier including an input terminal adapted to receive a RF signal, an output terminal adapted to output the RF signal after amplification therein, and at least one amplifier stage between the input and output terminals; providing a reference DC bias voltage to at least one said amplifier stage of the amplifier; detecting an overpeak voltage output of the amplifier at the output terminal wherein detecting the overpeak voltage comprises using a plurality of diodes connected in series with the output terminal of the amplifier; and reducing the reference DC bias voltage in response to the detected overpeak voltage using a clamping transistor that shunts current from an output terminal of a transistor of a bias circuit coupled to the at least one said amplifier stage. - View Dependent Claims (12, 13, 14, 15)
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16. An electronic circuit comprising:
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an amplifier including an input terminal adapted to receive a RF signal, an output terminal adapted to output the RF signal after amplification therein, and at least one amplifier stage between the input and output terminals, the at least one amplifier stage receiving a reference DC bias voltage; a first series of diodes coupled to the output terminal;
a bias transistor comprising an output terminal from which reference DC bias voltage is output; anda clamping transistor, wherein conduction by the clamping transistor depends on conduction by the first series of diodes, and conduction by the clamping transistor reduces the DC reference voltage output by the bias transistor. - View Dependent Claims (17, 18, 19, 20, 21, 22)
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23. An electronic circuit comprising:
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an amplifier including an input terminal adapted to receive a RF signal, an output terminal adapted to output the RF signal after amplification therein, and at least one amplifier stage between the input and output terminals, the at least one amplifier stage receiving a reference DC bias voltage; a first series of diodes, wherein a first of the diodes has an input terminal coupled to the output terminal of the amplifier, the first series of diodes being operable to conduct in response to an overpeak voltage at the output terminal of the amplifier; a second series of diodes, wherein a first of the diodes has an input terminal coupled to a ground and a last of the diodes has an output coupled to the output terminal of the amplifier; and a control circuit coupled to a node of the first series of diodes, and operable to reduce the reference DC voltage in response to conduction by the first series of diodes. - View Dependent Claims (24, 25)
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26. An electronic circuit comprising:
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an amplifier including an input terminal adapted to receive a RE signal, an output terminal adapted to output the RF signal after amplification therein, and at least one amplifier stage between the input and output terminals, the at least one amplifier stage receiving a reference DC bias voltage; a bias circuit providing the reference DC bias voltage to the at least one amplifier stage; and
a clamping transistor, wherein conduction by the clamping transistor depends on whether a voltage of the RE signal at the output terminal exceeds an overpeak voltage, and the conduction by the clamping transistor reduces the DC reference voltage provided to the at least one amplifier stage. - View Dependent Claims (27)
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Specification