Multi-Stage Power Amplifier Supply Split for Noise and Efficiency
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Solution Overview
Problem
Existing power amplifier circuits face inefficiencies when generating supply voltage, particularly at low battery voltages, and struggle to achieve high bandwidth and low noise, especially in applications like LTE and OFDM, due to limitations in linear and switching converters.
Innovation Solution
A circuit combining a switching converter and a low-dropout linear amplifier, where the switching converter provides peak power and the linear amplifier performs envelope tracking, allowing different stages of the power amplifier to use either voltage as supply, optimizing efficiency and bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a linear amplifier is used to generate supply voltage for power amplifier, then low noise and high bandwidth are achieved, but efficiency deteriorates when supply voltage is far below battery voltage
Solution Approach 1:
The power amplifier is divided into multiple stages, with different stages receiving different supply voltages. Final stages receive higher voltage from switching converter while earlier stages receive lower voltage from linear amplifier, segmenting the power delivery function to optimize both efficiency and noise performance across different operational requirements.
Solution Approach 2:
The supply voltage parameters are dynamically adjusted based on operational mode. The linear amplifier operates with variable output voltage to track the envelope signal, while switching converter provides adjustable peak voltage, allowing the system to adapt voltage levels to match battery voltage closely during high-power operation for improved efficiency.
2Loss of energy
If switching converter is used to generate supply voltage, then efficiency is improved, but bandwidth and noise performance deteriorate
Solution Approach 1:
The power amplifier stages are segmented such that final stages requiring high efficiency receive voltage from switching converter, while earlier stages requiring low noise and high bandwidth receive voltage from linear amplifier. This segmentation allows each converter type to operate in its optimal performance regime.
Solution Approach 2:
The linear amplifier acts as an intermediary between the switching converter and the power amplifier stages. It filters out switching noise and bandwidth limitations from the switching converter output, providing clean, high-bandwidth voltage to stages that require such performance while the switching converter handles the efficiency-critical peak power delivery.
3Reliability
If linear amplifier passes full load current to power amplifier, then supply voltage is maintained, but quiescent current increases reducing efficiency in high bandwidth applications
Solution Approach 1:
The current delivery function is segmented between two voltage sources. The switching converter delivers peak current for high-power demand periods, while the linear amplifier supplies current during lower-power periods and provides fine-tuned voltage regulation. This segmentation reduces the total current burden on the linear amplifier, lowering its quiescent current requirements.
Solution Approach 2:
The system dynamically switches between different voltage supply modes based on power demand. During high-power transmission, the switching converter provides peak voltage and current. During lower-power periods or when fine voltage control is needed, the linear amplifier takes over. This dynamic operation allows the linear amplifier to maintain supply voltage without continuously passing full load current, reducing quiescent current.
4Reliability
If linear amplifier is used in applications with high peak/average ratio, then supply voltage is maintained, but efficiency deteriorates due to high dropout
Solution Approach 1:
The voltage supply function is segmented between linear amplifier and switching converter based on peak/average power requirements. The switching converter handles peak power delivery with minimal dropout, while the linear amplifier maintains average voltage levels. This segmentation allows the system to efficiently handle high peak/average ratio signals by assigning each converter to its optimal operating range.
Solution Approach 2:
The output voltage parameters of both converters are dynamically changed based on the instantaneous power demand. The switching converter output voltage is adjusted to provide peak power when needed, while the linear amplifier output voltage is modulated to track the envelope signal. This parameter dynamic adjustment optimizes efficiency across the full dynamic range of high peak/average ratio applications.
Data Source
AI summary
A power amplifier is provided that includes a plurality of stages. Each of the stages is capable of being controlled by a first supply voltage or a second supply voltage. The first supply voltage is provided by a linear amplifier, and the second supply voltage is provided by a switching converter. A first stage is capable of being controlled by the first supply voltage, and a second stage is capable of being controlled by the second supply voltage.