Stacked Core-Device Power Amplifier for Low-Loss High-Voltage Output
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Solution Overview
Problem
Existing power amplifiers for high voltage and high frequency applications, such as those used in portable wireless devices, suffer from significant power losses due to the use of cascode devices with parasitic capacitances and lower transconductances, which are inefficient and noisy.
Innovation Solution
A power amplifier configuration featuring a stack of low voltage core devices, each with an individual breakdown voltage less than the battery voltage, connected in series between a first voltage terminal and ground, utilizing input and output capacitors and feedback elements to amplify low voltage signals to high voltage outputs, reducing power loss and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If cascode devices are used to achieve high voltage output, then the output voltage is improved, but power loss increases due to parasitic capacitances and lower transconductances
Solution Approach 1:
The patent divides the high voltage power amplifier into multiple low voltage amplifier stages connected in series. Each stage operates at a lower voltage level with optimized transconductance, avoiding the parasitic capacitance penalties of high voltage cascode devices. The segmented architecture allows each transistor to operate in its optimal voltage range while collectively achieving the required high voltage output.
Solution Approach 2:
The patent transitions from a single high voltage cascode architecture to a multi-stage low voltage stacked architecture. By adding the dimension of multiple series-connected stages, the system achieves high voltage output without requiring individual high voltage transistors, thereby avoiding their inherent parasitic capacitance problems.
2Stress or pressure
If cascode devices are used for high voltage operation, then the voltage swing is improved, but noise behavior deteriorates
Solution Approach 1:
By segmenting the amplification function across multiple low voltage stages, each stage contributes to the overall voltage swing without requiring high voltage operation. This segmentation allows each transistor to operate with lower noise characteristics inherent to low voltage devices, while the stacked configuration achieves the cumulative voltage swing needed.
3Reliability
If high voltage transistors are used, then the breakdown voltage is improved, but parasitic capacitance increases
Solution Approach 1:
The patent segments the voltage stress across multiple low voltage transistors connected in series. Each transistor experiences only a fraction of the total output voltage, well below its breakdown voltage, eliminating the need for high voltage transistors with their large parasitic capacitances. The series connection distributes the voltage stress appropriately.
Solution Approach 2:
The patent changes the operating voltage parameter of the transistors from high voltage to low voltage. By operating multiple low voltage transistors in series rather than using single high voltage transistors, the system achieves the required voltage handling capability while maintaining low parasitic capacitance characteristics.
Data Source
AI summary
A power amplifier includes an input terminal configured to receive a low voltage input signal, an output terminal configured to output a high voltage output signal, and a plurality of amplifiers stacked in series between a first voltage terminal and a second voltage terminal. Each of the amplifiers includes an input capacitor, an output capacitor, an input coupled to the input terminal through the input capacitor, an output coupled to the output terminal through the output capacitor, and a feedback element coupled between the input and the output of the amplifier.