Power amplifier circuit and high-frequency module
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Solution Overview
Problem
Existing power amplifier circuits face inefficiencies in high-frequency power gain linearity and power efficiency, particularly during envelope tracking, due to gain deviations and non-linearity in power-supply voltage variations.
Innovation Solution
A power amplifier circuit with a variable capacitor connected between the base and collector of an amplifier element, whose capacitance value decreases with increasing power-supply voltage, along with optional series resistors and diodes, to adjust gain deviations and enhance linearity of the power-supply control signal during envelope tracking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed power-supply voltage is used in the amplifier element, then the circuit operation is simple, but power efficiency is low during average power periods
Solution Approach 1:
The power-supply voltage to the amplifier element is dynamically changed in accordance with the envelope amplitude of the input signal. This dynamic voltage adjustment allows the amplifier to operate efficiently across different power levels, reducing power loss during average power periods while maintaining performance during peak periods.
Solution Approach 2:
The power-supply voltage parameter is varied based on the signal envelope amplitude. By changing this critical parameter dynamically rather than keeping it fixed, the system achieves improved power efficiency without requiring complex additional control mechanisms.
2Loss of energy
If the power-supply voltage is increased during envelope tracking, then power efficiency should improve, but gain deviation occurs due to non-linear power-supply control signal
Solution Approach 1:
A feedback mechanism is implemented where the power-supply voltage is adjusted based on the envelope amplitude of the input signal. This feedback loop ensures that the voltage changes precisely follow the signal envelope, maintaining linear gain characteristics while improving power efficiency.
Solution Approach 2:
The power-supply voltage parameter is changed in direct proportion to the envelope amplitude, ensuring linear relationship between control signal and output power. This parameter adjustment strategy resolves the gain deviation issue while maintaining power efficiency improvements.
3Manufacturing precision
If a variable capacitor with decreasing capacitance at higher voltage is used, then gain deviation increases and linearity improves, but device complexity increases
Solution Approach 1:
The variable capacitor is configured to automatically adjust its capacitance based on the applied voltage without requiring external control circuitry. The capacitor's inherent voltage-dependent characteristics provide the necessary gain adjustment, making the system self-regulating and reducing overall device complexity.
Solution Approach 2:
The capacitor's electrical parameter (capacitance) changes in response to voltage variations. This natural parameter change exploits the voltage-dependent behavior to achieve linear gain control, avoiding the need for complex active control mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration increases gain deviation in the linear gain region, improving the linearity of high-frequency power gain and power efficiency by adjusting gain automatically with power-supply voltage variations.
Implementation Method 1
a capacitance value of the variable capacitor decreases when the power-supply voltage is increased
Data Source
AI summary
A power amplifier circuit includes an amplifier element that amplifies a signal input to a base and outputs an amplified signal from a collector, and a variable capacitor provided between the base and the collector of the amplifier element. A power-supply voltage that varies in accordance with an envelope of amplitude of a radio-frequency signal is applied to the collector of the amplifier element, and capacitance of the variable capacitor decreases in response to an increase in the power-supply voltage input to the collector of the amplifier element.