Power Amplifier Bias Switching for Digital ET Gain Stability
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Solution Overview
Problem
In digital ET power amplifier circuits, the large gain difference due to variations in power supply voltage leads to degraded amplification characteristics and signal distortion.
Innovation Solution
A power amplifier circuit design that includes an amplifier transistor receiving first and second bias currents via a control terminal, with the second bias current being smaller than the first when a higher power supply voltage is applied, and a bias circuit that supplies these currents to reduce gain differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If digital ET method is used to optimize power-added efficiency, then power-added efficiency is improved, but amplification characteristics such as backoff and signal distortion are degraded due to large gain difference
Solution Approach 1:
The patent applies parameter changes by dynamically adjusting the bias current of the amplifier transistor based on the power supply voltage level. When the power supply voltage increases, the bias current is reduced accordingly, and when the power supply voltage decreases, the bias current is increased. This dynamic parameter adjustment compensates for the gain variation caused by digital ET voltage switching, thereby maintaining stable amplification characteristics while preserving the power-added efficiency benefits of digital ET operation
2Use of energy by moving object
If power supply voltage is varied to optimize efficiency, then power-added efficiency is improved, but gain difference increases causing signal distortion
Solution Approach 1:
The patent implements a feedback mechanism where the bias circuit monitors the power supply voltage level and automatically adjusts the bias current in response. The bias circuit receives the power supply voltage as input and generates an appropriate bias current that compensates for the voltage-induced gain variations. This closed-loop feedback control ensures that signal distortion is minimized while the power supply voltage continues to vary for efficiency optimization in digital ET mode
3Use of energy by moving object
If discrete voltage levels are used in digital ET, then power-added efficiency is improved, but amplification characteristics are degraded
Solution Approach 1:
The patent applies dynamics by transitioning from a static bias configuration to a dynamic bias adjustment system. The bias circuit is designed to automatically and dynamically adjust the bias current in real-time based on the discrete power supply voltage levels used in digital ET. This dynamic adaptation allows the amplifier to maintain optimal operating conditions across different voltage levels, preserving amplification characteristics while benefiting from the efficiency improvements of discrete voltage operation
Data Source
AI summary
A power amplifier circuit includes a power supply terminal and an amplifier transistor that has a base terminal, a collector terminal connected to the power supply terminal, and an emitter terminal and that performs power amplification of a radio-frequency input signal input through the base terminal to output a radio-frequency signal subjected to the power amplification from the collector terminal. The amplifier transistor receives first bias current via the base terminal assuming a first power supply voltage is applied to the power supply terminal and receives second bias current smaller than the first bias current via the base terminal assuming a second power supply voltage higher than the first power supply voltage is applied to the power supply terminal.