Split-Biased RF Power Amplifier for Improved Linearity
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Solution Overview
Problem
Existing RF power amplifiers (PAs) exhibit non-linear distortion in output signals as the RF input signal increases, despite the use of bias circuits, which affects the linearity and efficiency of the amplification process.
Innovation Solution
The RF PA configuration involves coupling a smaller first transistor with a larger second transistor, and a smaller first power cell with a significantly larger second power cell, where the second power cell is bias boosted to maintain consistent gain and phase, thereby enhancing linearity by adjusting current densities and voltage ratios between the transistors and power cells.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a bias circuit is used to improve linearity, then gain consistency is improved, but non-linear distortion still increases as RF input signal increases
Solution Approach 1:
The power amplifier is divided into multiple parallel power cells with different sizes (first power cell, second power cell, etc.). Each power cell processes a portion of the RF signal, allowing the system to maintain linearity across varying input signal levels by distributing the amplification task across multiple segments with different current densities.
Solution Approach 2:
Different power cells are designed with different sizes and operate at different current densities. The first power cell operates at a first current density while the second power cell operates at a second current density, creating local quality variations that optimize linearity performance across the entire signal range.
2Manufacturing precision
If the second power cell is made significantly larger than the first power cell, then linearity is enhanced, but device complexity increases
Solution Approach 1:
Multiple power cells are merged in parallel configuration, where the first power cell, second power cell, and additional power cells are combined to work together. This merging approach maintains signal linearity across different input levels while managing complexity through a systematic parallel architecture rather than a single complex cell.
Solution Approach 2:
The amplifier dynamically adapts its operation across different power cells based on the RF input signal level. As the input signal varies, different power cells contribute differently to the output, with larger power cells handling higher signal levels more efficiently, creating a dynamic response that maintains linearity without requiring complex external control circuits.
Data Source
AI summary
A radio frequency (RF) power amplifier (PA) may include a first transistor and a second transistor. A first power cell may be coupled with the first transistor, and a second power cell may be coupled with the second transistor. In embodiments, the first transistor may be scaled to operate at a first current density, while the second transistor may be scaled to operate at a second current density.