Stacked RF Amplifier Bias Switching Across Multiple Power Modes
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Solution Overview
Problem
Existing RF power amplifiers face challenges in efficiently managing RF signal amplification across multiple power modes, leading to potential out-of-band transmission and compliance issues due to incorrect power levels and distortion, particularly with silicon-on-insulator transistors that experience reduced performance under varying supply voltages.
Innovation Solution
A stacked amplifier configuration with a bias circuit that operates in multiple modes by biasing transistors to a linear region in one mode and as a switch in another, using silicon-on-insulator transistors and a supply control circuit to adjust voltage levels, allowing the amplifier to behave like a different number of transistors in the stack depending on the mode, thus optimizing performance across varying power modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a stacked amplifier configuration is used to handle multiple power modes, then the amplifier can operate across different power levels, but the transistors experience reduced performance and potential breakdown under varying supply voltages
Solution Approach 1:
The biasing circuit dynamically adjusts the operating point of transistors based on the active power mode. In first power modes, the second transistor is biased to a linear region of operation, while in second power modes, it is biased as a switch, allowing the amplifier to adapt its characteristics to different operating conditions and maintain reliability across varying supply voltages
Solution Approach 2:
The invention changes the biasing parameters of the transistors depending on the power mode. By adjusting the gate-source voltage and drain-source voltage of the second transistor based on the active power mode, the amplifier optimizes transistor performance for each mode, preventing breakdown and maintaining stable operation across different supply voltage levels
2Loss of energy
If the amplifier operates in multiple power modes with varying supply voltages, then power efficiency can be improved, but distortion and out-of-band transmission increase due to incorrect power levels
Solution Approach 1:
The biasing circuit dynamically switches between different biasing configurations based on the active power mode. This dynamic adjustment ensures that each transistor operates in the optimal region (linear or switching) for the current power mode, maintaining signal fidelity and preventing distortion while achieving power efficiency across different operating levels
Solution Approach 2:
Different transistors in the stacked configuration are biased with different characteristics depending on the power mode. The second transistor can be biased as a switch in low-power modes while other transistors maintain linear operation, creating localized optimal operating conditions for each transistor based on the overall power mode requirements
3Device complexity
If a fixed stacked amplifier configuration is used, then the circuit structure is simple, but the amplifier cannot optimize performance across varying power modes
Solution Approach 1:
The stacked amplifier configuration is designed to perform multiple functions across different power modes. The same physical transistor stack can operate with different biasing configurations, allowing a single circuit structure to serve both linear amplification and switching functions, thereby achieving multi-functionality without increasing hardware complexity
Data Source
AI summary
Aspects of this disclosure relate to an amplification circuit that includes a stacked amplifier and a bias circuit. The stacked amplifier includes at least a first transistor and a second transistor in series with each other. The stacked amplifier is operable in at least a first mode and a second mode. The bias circuit is configured to bias the second transistor to a linear region of operation in the first mode and to bias the second transistor as a switch in the second mode. In certain embodiments, the amplification circuit can be a power amplifier stage configured to receive a supply voltage that has a different voltage level in the first mode than in the second mode.