Cross-Coupled Power Amplifier Circuit for Stable Gain Tracking
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Solution Overview
Problem
In power amplifier circuits for wireless communication devices, especially in 5G systems, the high modulation bandwidth makes it difficult for envelope tracking systems to smoothly control the power-supply voltage, leading to discrete gain levels and reduced amplification efficiency due to strong power-supply voltage dependence.
Innovation Solution
A power amplifier circuit design that includes transistors with collector-base capacitance and additional capacitance circuits to reduce power-supply voltage dependence, allowing for continuous amplification by compensating feedback actions and maintaining gain stability across varying collector-base voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If envelope tracking is performed with discrete voltage control to improve power efficiency, then power efficiency is improved, but gain stability deteriorates due to strong power-supply voltage dependence
Solution Approach 1:
The patent applies feedback by connecting a capacitance circuit between the collector of one transistor and the base of another transistor in a differential amplifier configuration. This feedback mechanism compensates for gain variations caused by power-supply voltage changes, allowing the system to maintain stable gain while operating with discrete envelope tracking voltages, thus resolving the contradiction between power efficiency and gain stability.
Solution Approach 2:
The patent changes the electrical parameters of the circuit by introducing capacitance circuits that alter the voltage relationships between transistors. These parameter changes create a compensatory effect where the capacitance circuits counteract the gain variations induced by discrete power-supply voltage steps, enabling both power efficiency improvement and gain stability maintenance.
2Speed
If stepped power-supply voltage is used to match high modulation bandwidth, then bandwidth compatibility is improved, but amplification smoothness deteriorates due to discrete gain levels
Solution Approach 1:
The feedback connection through the capacitance circuit creates a compensatory mechanism that smooths out the discrete gain changes caused by stepped power-supply voltage. The feedback loop detects gain variations and counteracts them, allowing the system to handle high modulation bandwidths while maintaining smooth analog-like amplification characteristics.
Solution Approach 2:
The capacitance circuit creates an equipotential relationship between the collector of one transistor and the base of another, effectively equalizing the voltage variations caused by stepped power supply. This equipotential effect ensures that all transistors experience similar voltage conditions, maintaining amplification smoothness across the entire bandwidth range.
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
The design achieves reduced power-supply voltage dependence, enabling smooth power amplification and preventing harmonic components from modulating into the high-frequency signal, thus enhancing linearity and reducing gain variations, even with discrete voltage changes.
Implementation Method 1
a first capacitance circuit electrically connected between the collector of the second transistor and the base of the first transistor; and a second capacitance circuit electrically connected between the collector of the first transistor and the base of the second transistor
Data Source
AI summary
A power amplifier circuit includes a first transistor having an emitter electrically connected to a common potential, a base to which a first high-frequency signal is input, and a collector from which a third high-frequency signal is output; a second transistor having an emitter electrically connected to the common potential, a base to which a second high-frequency signal is input, and a collector from which a fourth high-frequency signal is output; a first capacitance circuit electrically connected between the collector of the second transistor and the base of the first transistor; and a second capacitance circuit electrically connected between the collector of the first transistor and the base of the second transistor.