Bias Circuit Temperature Compensation for Stable Gain and EVM
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Solution Overview
Problem
Typical amplifying devices face challenges with temperature changes, leading to variations in gain and linearity characteristics, particularly in 5G communications, where a low Error Vector Magnitude (EVM) is required, and existing temperature compensation methods either increase production costs or have limited effectiveness due to complex circuit structures.
Innovation Solution
A bias circuit with a temperature compensation circuit, utilizing resistors with specific thermal coefficients to maintain stable base current and reduce base bias current, ensuring consistent performance across temperature variations, thereby improving gain flatness and EVM.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a separate temperature compensation circuit is added to the amplifying device, then temperature compensation function is improved, but production cost increases
Solution Approach 1:
The patent merges the temperature compensation function with the existing bias circuit by integrating temperature compensation components (resistors with different thermal coefficients) into the bias circuit structure. This combination eliminates the need for a separate temperature compensation circuit, thereby maintaining effective temperature compensation while reducing production costs and circuit complexity.
2Reliability
If the bias circuit includes a temperature compensation function, then temperature compensation is achieved, but the circuit structure becomes complex with more components
Solution Approach 1:
The temperature compensation function is merged into the bias circuit by utilizing existing bias circuit components and adding minimal temperature compensation components (resistors with different thermal coefficients). This integration approach achieves effective temperature compensation while avoiding the complexity of a separate compensation circuit.
Solution Approach 2:
The bias circuit is designed to serve multiple functions: providing bias current to the amplifier and simultaneously performing temperature compensation. By making the bias circuit multi-functional, the patent eliminates the need for dedicated temperature compensation components, thereby simplifying the overall circuit structure.
3Device complexity
If typical bias circuits are used without temperature compensation, then circuit structure is simple, but gain and EVM change with temperature
Solution Approach 1:
The patent utilizes resistors with different thermal coefficients (positive and negative thermal coefficients) to compensate for temperature-induced parameter changes in the amplifier. By carefully selecting and combining resistors with opposite thermal characteristics, the circuit maintains stable gain and EVM across temperature variations while keeping the overall structure relatively simple.
Solution Approach 2:
The temperature compensation mechanism works by creating a feedback loop where the voltage changes across resistors with different thermal coefficients counteract the temperature-induced changes in amplifier characteristics. This automatic feedback mechanism maintains stable amplifier performance without requiring complex external control systems.
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 solution effectively compensates for temperature-induced changes in amplifying devices, enhancing linearity and reducing production costs by simplifying the circuit structure while maintaining accurate temperature compensation.
Implementation Method 1
a second resistor in the second current path, and connected between an emitter of the second transistor and a base of the first transistor and having a first thermal coefficient, and a third resistor included in the second current path, and connected between the base of the first transistor and the ground and having a second thermal coefficient, different from the first thermal coefficient
Data Source
AI summary
A bias circuit includes a bias current circuit and a temperature compensation circuit. The bias current circuit includes a first resistor and a first transistor, in a first current path connected between a current terminal of a reference current and a ground, and connected to each other in series, and a second transistor in a second current path connected between the current terminal and the ground, and having a base connected to a collector of the first transistor. The temperature compensation circuit includes a second resistor in the second current path, and connected between an emitter of the second transistor and a base of the first transistor and having a first thermal coefficient, and a third resistor included in the second current path, and connected between the base of the first transistor and the ground and having a second thermal coefficient, different from the first thermal coefficient.