Multi-Finger FET Power Amplifier Thermal Linearity Control
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Solution Overview
Problem
Power amplifiers using multi-finger FETs experience degradation in linearity due to thermal effects, leading to the formation of loop currents and kink phenomena, which existing temperature compensation techniques, such as those involving modularized temperature sensors and operational amplifiers, are unsuitable for addressing effectively.
Innovation Solution
A power amplifier configuration that includes temperature detectors for FET channels and the substrate, detection circuits converting temperature differences to thermoelectromotive force, and a comparator to control switches based on these differences, ensuring that the gate of the cooler FET is connected to the input, thereby preventing loop currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If temperature sensors are provided on modularized casings to detect FET channel temperatures, then temperature detection capability is improved, but delay time in detecting temperature changes occurs and control cannot be exercised effectively
Solution Approach 1:
The patent uses the substrate temperature as an intermediary parameter to represent FET channel temperature. Instead of directly measuring FET channel temperature with separate sensors, the substrate temperature detector measures the substrate temperature which correlates with FET channel temperature, eliminating the need for direct FET mounting and reducing detection delay.
2Reliability
If temperature sensors and operational amplifiers are added to compensate temperature differences, then temperature balance control is improved, but device complexity increases and additional power is required
Solution Approach 1:
The patent merges the temperature detection and control functions into the existing substrate structure. The substrate serves both as the FET mounting platform and as the temperature sensing element, eliminating the need for separate temperature sensors and operational amplifiers, thus reducing device complexity while maintaining temperature balance control.
Solution Approach 2:
The substrate is given multiple functions: it serves as the mechanical support for FETs, the thermal conduction path, and the temperature sensing element. This multi-functionality eliminates the need for dedicated temperature sensors and reduces overall device complexity.
3Temperature
If gate pitch of multi-finger FETs is increased and redundant regions are provided to radiate heat, then temperature rise in FET channels is mitigated, but area of power amplifier increases
Solution Approach 1:
The substrate automatically serves as the heat radiation path without requiring additional redundant regions or heat sinks. The substrate's inherent thermal conduction properties are utilized to conduct heat away from FET channels, eliminating the need for extra space-consuming heat dissipation structures.
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 suppresses the degradation of linearity caused by thermal effects, maintaining the power amplifier's performance and preventing loop currents, as demonstrated by improved output characteristics and efficiency compared to comparative examples.
Implementation Method 1
a first detection circuit which detects a difference between an output of the first temperature detector and an output of the third temperature detector and converts the difference to thermoelectromotive force; a second detection circuit which detects a difference between an output of the second temperature detector and the output of the third temperature detector and converts the difference to thermoelectromotive force
Data Source
AI summary
A power amplifier includes: a first multi-finger FET formed on a semiconductor substrate; a second multi-finger FET formed on the semiconductor substrate; a first temperature detector which detects a channel temperature of the first FET; a second temperature detector which detects a channel temperature of the second FET; a third temperature detector which detects a temperature of the semiconductor substrate; a first detection circuit detecting a difference between an output of the first temperature detector and an output of the third temperature detector and converting the difference to thermoelectromotive force; a second detection circuit detecting a difference between an output of the second temperature detector and the output of the third temperature detector and converting the difference to thermoelectromotive force; and a comparator comparing outputs of the first and second detection circuits with each other to turn on one of the first and second switches and turn off the other.