Stacked Transistor Gate Biasing for Variable-Supply Linearity
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Solution Overview
Problem
Existing amplifiers face inefficiencies when operating with variable supply voltages, particularly in envelope tracking mode, where maintaining linearity and efficiency is challenging due to dynamic changes in supply voltage, leading to unwanted distortion and heat dissipation.
Innovation Solution
A circuital arrangement with stacked transistors and a gate bias circuit that provides fixed and variable bias voltages to maintain constant drain voltage and equal drain-to-source voltage across transistors, ensuring efficient operation across varying supply voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If variable supply voltage is used in envelope tracking mode, then power efficiency is improved, but linearity deteriorates causing distortion
Solution Approach 1:
The patent applies dynamics by making the gate bias voltages variable rather than fixed. The gate bias circuit dynamically adjusts the gate voltages of stacked transistors in response to changes in supply voltage, allowing the amplifier to maintain linearity across a wide range of supply voltages while operating in envelope tracking mode for improved power efficiency.
Solution Approach 2:
The patent changes the parameter of gate bias voltage from constant to variable. By adjusting gate voltages based on supply voltage conditions, the system maintains optimal transistor operating points across varying supply voltages, preserving linearity while enabling efficient variable supply operation.
2Device complexity
If fixed gate bias voltage is used, then circuit complexity is reduced, but adaptability to variable supply voltage deteriorates
Solution Approach 1:
The patent segments the gate bias control into separate controllable elements. Instead of a single fixed bias voltage, the system provides individual gate bias voltages for each transistor in the stacked configuration, allowing independent adjustment of each transistor's operating point to adapt to variable supply conditions.
Solution Approach 2:
The gate bias circuit acts as an intermediary between the variable supply voltage and the transistor gates. It translates supply voltage changes into appropriate gate voltage adjustments, enabling the transistors to adapt their operating points without direct connection to the variable supply, thus maintaining adaptability while managing complexity.
3Loss of energy
If variable supply voltage is applied to stacked transistors, then power efficiency is improved, but voltage distribution uniformity deteriorates
Solution Approach 1:
The patent applies local quality by providing different gate bias voltages to different transistors in the stack. Each transistor receives a customized gate voltage tailored to its position and characteristics, ensuring uniform voltage distribution and consistent operating conditions across all transistors even when the supply voltage varies.
Data Source
AI summary
Various methods and circuital arrangements for biasing one or more gates of stacked transistors of an amplifier are presented, where the amplifier can have a varying supply voltage. According to one aspect, the gate of the input transistor of the amplifier is biased with a fixed voltage whereas the gates of the other transistors of the amplifier are biased with variable voltages that are linear functions of the varying supply voltage. According to another aspect, the linear functions are such that the variable voltages coincide with the fixed voltage at a value of the varying supply voltage for which the input transistor is at the edge of triode. According to another aspect, biasing of the stacked transistors is such that, while the supply voltage varies, the drain-to-source voltage of the input transistor is maintained to a fixed value whereas the drain-to-source voltages of all other transistors are equal to one another.