Power Amplifier Bias Switching for Linearity and Power Tracking
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Solution Overview
Problem
Power amplifier modules in mobile communication devices face challenges in maintaining high linearity across wide dynamic ranges while minimizing power consumption, especially when operating in multiple modes such as envelope tracking and average power tracking.
Innovation Solution
The power amplifier module incorporates a bias circuit with first and second transistors and resistors, controlled by distinct bias control voltages to adjust bias current based on operation modes, allowing for optimal bias supply in various operation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a high power supply voltage is used to maintain high linearity across wide dynamic range, then linearity is improved, but power consumption increases
Solution Approach 1:
The bias circuit dynamically adjusts the bias control voltage based on operation mode signals (envelope tracking vs average power tracking), allowing the power amplifier to adapt its operating characteristics. This dynamic adjustment enables high linearity when needed while reducing power consumption during normal operation, resolving the contradiction between maintaining precision and managing energy use.
Solution Approach 2:
The invention changes the bias control voltage parameter based on different operation modes. By switching between different bias voltage levels and characteristics depending on whether envelope tracking or average power tracking is active, the system achieves high linearity only when required while minimizing power consumption during standard operation.
2Use of energy by moving object
If envelope tracking technique is used to improve power efficiency, then power consumption is reduced, but linearity may deteriorate in certain operation modes
Solution Approach 1:
The bias circuit switches between envelope tracking mode and average power tracking mode dynamically based on operating conditions. This allows the system to use envelope tracking for power efficiency when appropriate while switching to average power tracking when linearity is prioritized, resolving the contradiction between power consumption and linearity maintenance.
3Device complexity
If a single bias circuit configuration is used for all operation modes, then device complexity is reduced, but adaptability to different operation modes deteriorates
Solution Approach 1:
The bias circuit is segmented into multiple parallel paths with different transistor configurations (first transistor with first ballast resistor, second transistor with second ballast resistor). Each path is optimized for specific operation modes, allowing the circuit to adapt to different modes while maintaining manageable complexity through modular design.
Solution Approach 2:
The bias circuit achieves multi-functionality by incorporating multiple transistor-resistor paths that can be selectively activated. The same bias circuit structure serves both envelope tracking mode and average power tracking mode by switching between different internal configurations, providing adaptability without requiring entirely separate circuits for each mode.
Data Source
AI summary
A power amplifier module includes an amplifier transistor and a bias circuit. A first power supply voltage based on a first operation mode or a second power supply voltage based on a second operation mode is supplied to the amplifier transistor. The amplifier transistor receives a first signal and outputs a second signal obtained by amplifying the first signal. The bias circuit supplies a bias current to the amplifier transistor. The bias circuit includes first and second resistors and first and second transistors. The first transistor is connected in series with the first resistor and is turned ON by a first bias control voltage which is supplied when the first operation mode is used. The second transistor is connected in series with the second resistor and is turned ON by a second bias control voltage which is supplied when the second operation mode is used.