Voltage bias and temperature compensation circuit for radio frequency power amplifier
First Claim
Patent Images
1. A radio frequency (RF) power amplifier, comprising:
- a radio frequency gain stage for providing an amplified RF signal to an antenna at an RF antenna power output level, the radio frequency gain stage including a depletion mode MESFET (metal epitaxial semiconductor field effect transistor) configured for amplifying an RF signal to provide the amplified RF signal, the depletion mode MESFET being characterized by a MESFET temperature coefficient; and
a bias circuit having a control input for receiving a variable control signal and an output coupled to the radio frequency gain stage, the bias circuit providing an output voltage to the radio frequency gain stage in response to the variable control signal, the output voltage having an output voltage temperature coefficient, the output voltage temperature coefficient substantially compensating the MESFET temperature coefficient to maintain the RF antenna power output level substantially constant.
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Abstract
A communication device (104) includes a radio frequency power amplifier (202) and a bias circuit (204). The power amplifier (202) includes a depletion mode MESFET (214) for RF power amplification. To properly bias the MESFET (214) in a circuit including logic components powered by a conventional battery (136), the bias circuit (204) includes a level shifter (223) to provide the necessary gate-to-source voltage for the MESFET (214). To maintain the RF output power from the communication device (104) constant over temperature, the bias circuit (204) output voltage varies over temperature to track the temperature variation of the MESFET (214).
89 Citations
7 Claims
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1. A radio frequency (RF) power amplifier, comprising:
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a radio frequency gain stage for providing an amplified RF signal to an antenna at an RF antenna power output level, the radio frequency gain stage including a depletion mode MESFET (metal epitaxial semiconductor field effect transistor) configured for amplifying an RF signal to provide the amplified RF signal, the depletion mode MESFET being characterized by a MESFET temperature coefficient; and a bias circuit having a control input for receiving a variable control signal and an output coupled to the radio frequency gain stage, the bias circuit providing an output voltage to the radio frequency gain stage in response to the variable control signal, the output voltage having an output voltage temperature coefficient, the output voltage temperature coefficient substantially compensating the MESFET temperature coefficient to maintain the RF antenna power output level substantially constant. - View Dependent Claims (2, 3)
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4. A radio frequency (RF) power amplifier, comprising:
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a radio frequency gain stage for providing an amplified RF signal to an antenna at an RF antenna power output level, the radio frequency gain stage including a depletion mode MESFET (metal epitaxial semiconductor field effect transistor) configured for amplifying an RF signal to provide the amplified RF signal and characterized by a MESFET temperature coefficient; and a bias circuit having a control input for receiving a variable control signal and an output coupled to the radio frequency gain stage, the bias circuit providing an output voltage to the radio frequency gain stage in response to the variable control signal, the output voltage having an output voltage temperature coefficient sufficient to maintain the RF antenna power output level substantially constant; wherein the output voltage temperature coefficient substantially compensates the MESFET temperature coefficient and wherein the depletion mode MESFET requires biasing by a negative gate-to-source voltage and the variable control signal comprises a positive voltage, and wherein the bias circuit includes a level shifter for receiving the positive voltage and producing the output voltage suitable for biasing the depletion mode MESFET.
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5. A communication device, comprising:
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an antenna; a radio frequency (RF) power amplifier coupled to the antenna for providing amplified RF signals to the antenna at an RF antenna power output level, the RF power amplifier having a temperature variation; a bias circuit coupled to the RF power amplifier, the bias circuit having a control input for receiving a positive control voltage and an output coupled to the RF power amplifier, the bias circuit producing a negative output voltage in response to the positive control voltage, the negative output voltage being temperature compensated to substantially cancel the temperature variation of the RF power amplifier for maintaining the RF antenna power output level at a substantially constant value; and a controller coupled to the bias circuit for providing the positive control voltage to the bias circuit for controlling the RF antenna power output level. - View Dependent Claims (6, 7)
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Specification