Power Amplifier Gain Compensation Using Differential Temperature Sensing
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Solution Overview
Problem
Amplifiers experience gain droop and variation due to self-heating, leading to degradation in error vector magnitude (EVM), which is challenging to compensate for using existing techniques that require external components or fixed RC delays, limiting their performance in wireless communication networks.
Innovation Solution
An amplifier circuit incorporating a temperature sensor circuit with differential paths and resistors to generate an output voltage proportional to temperature differences, which is used to modulate the bias current and maintain consistent gain through heating, eliminating the need for external components and allowing for dynamic gain compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing compensation techniques using external components or fixed RC delays are used, then gain compensation can be achieved, but device complexity and sensitivity to environmental factors increase
Solution Approach 1:
The temperature sensor circuit is integrated directly into the amplifier circuit, merging the temperature sensing function with the existing amplifier structure. This eliminates the need for separate external temperature sensors and reduces overall device complexity while maintaining effective gain compensation through the differential transistor arrangement.
Solution Approach 2:
The amplifier circuit uses its own internal temperature characteristics to generate the compensation signal. The differential transistor pair leverages the temperature difference between the amplifier transistor and the thermally isolated sensor transistor to automatically generate the compensation voltage, making the circuit self-regulating without external control components.
2Reliability
If external components or large capacitors are used for gain compensation, then performance standards can be met, but device area and complexity increase
Solution Approach 1:
The circuit uses standard, readily available transistor and resistor components that can be easily fabricated using existing CMOS or bipolar processes. These conventional components replace the need for specialized external components or large capacitors, reducing both area and cost while achieving the required EVM performance through the differential temperature sensing approach.
3Ease of manufacture
If fixed RC delays are used for compensation, then implementation is simple, but adaptability to different operating conditions is limited
Solution Approach 1:
The compensation circuit dynamically adapts to changing operating conditions by continuously monitoring the temperature difference between the amplifier transistor and the thermally isolated sensor transistor. This dynamic temperature-based compensation mechanism replaces fixed RC delays, providing automatic adaptation to various environmental conditions while maintaining ease of implementation through the differential circuit architecture.
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 gain droop, achieving improved linearity and reduced EVM, meeting high performance standards for Wi-Fi communications without requiring external dies or large capacitors, and is less sensitive to environmental factors.
Implementation Method 1
a second transistor thermally linked to the amplifier and being configured to sense a temperature at the amplifier
Implementation Method 2
a first transistor thermally isolated from the amplifier and being configured to sense an ambient temperature
Data Source
AI summary
According to at least one example, an amplifier circuit includes an amplifier and a temperature sensor circuit. The temperature sensor circuit includes a first transistor thermally isolated from the amplifier and being configured to sense an ambient temperature, and a second transistor thermally linked to the amplifier and being configured to sense a temperature at the amplifier, the temperature sensor circuit being a differential circuit having a first path and a second path with the first and second transistors being arranged on the first and second paths of the differential circuit respectively. The temperature sensor circuit is configured to generate an output voltage inversely proportional to a temperature difference between the ambient temperature and the temperature at the amplifier.