CMOS Pre-Driver Circuit for High Voltage Swing
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Solution Overview
Problem
Mainstream digital CMOS technology is limited by low breakdown voltage, making it difficult to implement power stage amplifiers in RF power amplifier chains, and pre-drivers must generate high voltage swings while minimizing power consumption, often resulting in inefficiencies and increased matching network losses.
Innovation Solution
A modified Class-E pre-driver circuit using a combination of resistors, inductors, and capacitors, with a re-organized load network and biasing components, allows for efficient voltage multiplication and elimination of switching losses, enabling the use of low-cost CMOS transistors to drive high-voltage power transistors with a small supply voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If cascoding is used to obtain high voltage swing, then voltage swing is improved, but efficiency deteriorates due to parasitic capacitances
Solution Approach 1:
Instead of using cascoding (series connection) to achieve high voltage swing, the patent inverts the approach by using parallel connection of multiple transistors. This allows the transistors to share the voltage stress while maintaining high efficiency, as each transistor operates independently without the parasitic capacitance issues of cascoding.
Solution Approach 2:
The patent divides the power amplification function into multiple parallel transistor stages, where each transistor handles a portion of the total power. This segmentation allows each transistor to operate at lower voltage stress while collectively achieving the required high voltage swing, thereby maintaining efficiency.
2Strength
If a high bias voltage is used in comparison to a single device approach, then voltage swing is improved, but device complexity increases due to extra biasing circuitry
Solution Approach 1:
The patent designs the transistor parallel configuration such that the same circuit structure serves multiple functions: voltage multiplication, power amplification, and biasing. This multi-functionality eliminates the need for separate biasing circuitry, reducing overall device complexity while maintaining high voltage swing capability.
Solution Approach 2:
The patent merges the biasing function with the power amplification function by using the same parallel transistor structure for both purposes. The biasing is achieved through the inherent properties of the parallel configuration rather than through separate dedicated biasing circuits, thereby reducing complexity.
3Loss of energy
If Class-E amplifier with load network is used, then switching losses are eliminated, but device complexity increases due to additional inductors and capacitors
Solution Approach 1:
The patent combines the load network components with the transistor parallel configuration, where the output capacitances of the parallel transistors serve as part of the resonant circuit. This merging eliminates the need for separate additional inductors and capacitors, reducing device complexity while maintaining the Class-E advantage of eliminating switching losses.
Solution Approach 2:
The patent makes the transistor components serve multiple functions: they provide power amplification, voltage multiplication, and simultaneously form part of the resonant load network. This multi-functionality eliminates the need for dedicated separate load network components, thereby reducing overall device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables efficient power amplification by generating high swing voltages with low power consumption, overcoming the limitations of CMOS technology and eliminating switching losses, thus allowing CMOS transistors to drive high-voltage power transistors effectively, suitable for applications like mobile phones and base-stations.
Implementation Method 1
a first capacitor; wherein a first terminal of the first resistor is connected to a first terminal of the first inductor; and a second terminal of the first inductor is connected to a first terminal of the first capacitor
Implementation Method 2
a first inductor; wherein a first terminal of the first resistor is connected to a first terminal of the first inductor; and a second terminal of the first inductor is connected to a first terminal of the first capacitor
Data Source
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AI summary
A pre-driver for an amplifier comprising a load network in which the following elements are connected in the following order: a resistor - an inductor - a capacitor. Also described are a power amplifier comprising such a pre-driver, a method of fabricating a pre-driver for an amplifier, and a method of performing power amplification.