Segmented Envelope Tracking Amplifier for Lower Quiescent Current
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Solution Overview
Problem
Traditional power amplifiers in wireless communication devices are power-hungry due to their fixed supply voltage, leading to significant power loss as heat, especially when operating at non-peak RF output power conditions, and require high quiescent current for wide-bandwidth envelope tracking, which further increases power consumption.
Innovation Solution
An envelope tracking supply modulator using a linear amplifier with a segmented output stage, where the number of amplifiers involved in setting the modulated supply voltage is adjusted based on the power amplifier's output power level, reducing quiescent current consumption by enabling or disabling amplifiers depending on the power mode, thereby optimizing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed supply voltage is used for the power amplifier, then the circuit is simple, but significant power is lost as heat when operating at non-peak RF output power conditions
Solution Approach 1:
The patent implements envelope tracking by dynamically modulating the supply voltage of the power amplifier according to the envelope of the RF input signal. This allows the PA to operate closer to its peak efficiency point across varying output power levels, dramatically reducing power dissipation as heat while maintaining adaptability through dynamic voltage adjustment
2Speed
If a typical linear amplifier is used for wide-bandwidth envelope tracking, then the bandwidth is sufficient, but large quiescent current is consumed
Solution Approach 1:
The output stage circuit is divided into multiple parallel amplifier paths (first amplifier path, second amplifier path, etc.). Each path can be independently controlled and enabled/disabled based on the required output power level. This segmentation allows the system to use only the necessary number of amplifiers for the current operating condition, reducing quiescent current consumption while maintaining wide bandwidth capability when needed
Solution Approach 2:
The system dynamically selects and enables specific amplifier paths based on the envelope signal level and required output power. This dynamic configuration allows the linear amplifier to adapt its bandwidth and current consumption characteristics to match the instantaneous signal requirements, reducing power consumption during low-power operations while maintaining wide bandwidth when high power is needed
Data Source
AI summary
A linear amplifier of an envelope tracking supply modulator includes a pre-driver stage circuit and an output stage circuit. The pre-driver stage circuit receives an envelope input, and generates a pre-driver output according to the envelope input. The output stage circuit receives the pre-driver output, and generates an amplifier output according to the pre-driver output. The amplifier output is involved in setting a modulated supply voltage of a power amplifier. The output stage circuit has a plurality of amplifiers, including a first amplifier and a second amplifier. When the power amplifier has a first output power level, the first amplifier is involved in setting the amplifier output, and the second amplifier is not involved in setting the amplifier output. When the power amplifier has a second output power level different from the first output power level, the first amplifier and the second amplifier are involved in setting the amplifier output.