Stacked RF Power Amplifier Biasing Across Variable Supply Modes
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Solution Overview
Problem
Existing RF power amplifiers face challenges in efficiently managing power modes with significant differences in supply voltage, leading to reduced performance in terms of output 1 dB compression point, saturated power, and power-added efficiency due to early power compression and hot carrier injection issues.
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, allowing for reduced drain-to-source voltage and improved performance across varying power modes, using silicon-on-insulator transistors and a supply control circuit for voltage adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stacked amplifier configuration is used to handle high supply voltages, then the breakdown voltage capability is improved, but the power-added efficiency deteriorates due to early power compression
Solution Approach 1:
The amplifier is divided into multiple stacked transistor stages, where each transistor handles a portion of the total voltage. This segmentation allows the system to achieve high breakdown voltage capability while maintaining efficiency by optimizing each stage's operating point independently
Solution Approach 2:
The biasing circuit dynamically adjusts the operating point of the stacked transistors based on the supply voltage level and power mode. This dynamic adaptation prevents early power compression by ensuring each transistor operates in its optimal region, thereby maintaining power-added efficiency across varying voltage conditions
2Use of energy by moving object
If the supply voltage is reduced for lower power modes, then the energy consumption is improved, but the output power capability deteriorates
Solution Approach 1:
The biasing circuit dynamically reconfigures the transistor operating points based on the active power mode. In lower power modes with reduced supply voltage, the circuit adjusts biasing to maintain optimal performance, preventing early compression and preserving output power capability relative to the available supply
Solution Approach 2:
The circuit changes operating parameters (bias voltages and currents) according to the supply voltage level. By adapting these parameters dynamically, the amplifier maintains efficient operation and preserved output capability across different power modes despite voltage variations
3Device complexity
If a fixed biasing configuration is used, then the circuit complexity is reduced, but the adaptability to different power modes deteriorates
Solution Approach 1:
The biasing circuit is designed to perform multiple functions: it automatically adapts to different supply voltage levels and power modes without requiring separate biasing circuits for each mode. This multi-functionality provides mode adaptability while avoiding the complexity of multiple dedicated biasing networks
Solution Approach 2:
The biasing circuit automatically senses the operating conditions and self-adjusts the transistor biasing points accordingly. This self-service capability enables adaptation to different power modes without complex external control, balancing adaptability with circuit simplicity
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.