Power Amplifier Bias Layout for Thermal Gain Stability
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Solution Overview
Problem
Existing power amplifier circuits experience a decrease in gain due to temperature increases, particularly in the amplifying stage transistor, leading to reduced collector current and efficiency, especially when the power supply voltage is high, as a result of self-heating and temperature compensation mechanisms that suppress collector current.
Innovation Solution
A power amplifier design featuring a first and second transistor group connected in parallel, with a third transistor providing bias current and a voltage supply circuit using diodes or transistors to maintain a lower voltage at the transistor base, ensuring strong thermal coupling between the third transistor and the transistor groups, reducing the distance between them compared to the voltage supply circuit, thereby minimizing gain decrease with output power increase.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a power supply voltage increases to improve output power, then output power is improved, but power-added efficiency decreases and temperature increase due to self-heating increases
Solution Approach 1:
The patent changes the voltage parameter dynamically by introducing a voltage supply circuit that adjusts the power supply voltage to the amplifying stage transistor based on temperature conditions. When temperature increases due to self-heating, the circuit supplies a lower voltage to compensate, thereby maintaining efficiency while allowing high output power operation.
2Stability of the object's composition
If a temperature compensation function is added to suppress collector current increase with temperature, then temperature stability is improved, but gain decreases more remarkably
Solution Approach 1:
The patent applies local quality by providing different voltage supply conditions to different parts of the circuit. The voltage supply circuit is specifically coupled to the amplifying stage transistor to provide localized voltage adjustment, while other parts of the circuit operate with standard voltage supply. This localized approach maintains gain in non-critical areas while stabilizing temperature-critical areas.
3Stability of the object's composition
If the voltage supply circuit is disposed close to the amplifying stage transistor to improve temperature compensation, then temperature compensation effectiveness is improved, but collector current suppressing effect is enhanced and gain decreases further
Solution Approach 1:
The patent introduces an intermediary element - a control circuit that mediates between the temperature compensation function and the voltage supply. The control circuit detects temperature conditions and selectively adjusts the voltage supply to the amplifying stage transistor, acting as an intermediary that prevents direct excessive suppression of collector current while still providing temperature compensation.
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 effectively reduces the decrease in gain at higher output powers by promoting collector current increase and maintaining efficiency, while preventing thermal runaway and destruction of the power stage.
Implementation Method 1
a first voltage supply circuit including at least one of a first diode and an eleventh transistor, for supplying a lower voltage to a base of the third transistor as a temperature of the first diode or the eleventh transistor is higher
Implementation Method 2
a third transistor for supplying a bias current to a base of the first transistor group
Implementation Method 3
a first transistor group including a plurality of unit transistors connected in parallel for amplifying and outputting a radio frequency signal, a second transistor group including a plurality of unit transistors connected in parallel for amplifying and outputting an output signal from the first transistor group
Data Source
AI summary
A power amplifier including a first transistor for amplifying and outputting a radio frequency signal, a second transistor, a third transistor for supplying a bias current, a first voltage supply circuit for supplying a lower voltage to a base of the third transistor as a temperature of a first diode is higher. The third transistor and the first transistor, or the third transistor and the second transistor, are disposed without another electronic element interposed therebetween. The third transistor is disposed such that a distance between the third transistor and the first transistor is smaller than a distance between the first voltage supply circuit and the first transistor, or a distance between the third transistor and the second transistor is smaller than a distance between the first voltage supply circuit and the second transistor.