Injection-Locked RF Amplifier With Stacked Output Stage for Variable Supply
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Solution Overview
Problem
RF amplifiers face challenges in efficiently amplifying radio frequency signals across multiple power modes due to varying supply voltages, leading to reduced power-added efficiency and output 1 dB compression point, especially in silicon-on-insulator (SOI) power amplifier applications with stacked transistor topologies.
Innovation Solution
The implementation of an RF amplifier with an injection-locked oscillator driver stage and a stacked output stage featuring a transistor stack, including at least two transistors in series, allows for adjustable supply voltage based on operational modes, maintaining high efficiency across different power modes by biasing transistors differently depending on the mode of operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a stacked transistor topology is used in RF amplifiers, then the breakdown voltage is increased, but the power-added efficiency and output 1 dB compression point are reduced
Solution Approach 1:
The amplifier is divided into two separate stages: a driver stage and a stacked output stage. The driver stage processes the input signal and generates an intermediate amplified signal, while the stacked output stage provides the final power amplification. This segmentation allows each stage to be optimized independently, with the driver stage operating at lower voltages for efficiency and the stacked output stage providing voltage multiplication for high breakdown voltage tolerance.
Solution Approach 2:
The driver stage acts as an intermediary between the input signal and the stacked output stage. It conditions the input signal and provides an intermediate amplified signal that is then fed to the stacked output stage, which performs the final power amplification. This intermediary stage allows the system to achieve both efficiency and high voltage capability.
2Strength
If a stacked transistor topology is used, then the voltage handling capability is improved, but the headroom is reduced
Solution Approach 1:
By segmenting the amplifier into driver and output stages, the voltage requirements are distributed across stages rather than requiring a single transistor to handle the full voltage swing. The stacked output stage handles high voltage while the driver stage operates with adequate headroom.
Solution Approach 2:
The problem is solved by adding a temporal dimension to the amplification process through multi-stage operation. Rather than requiring a single transistor to simultaneously provide both voltage handling and headroom, the signal progresses through stages at different times, with each stage optimized for its specific function.
3Adaptability or versatility
If the supply voltage is varied for different power modes, then the adaptability is improved, but the power-added efficiency deteriorates
Solution Approach 1:
The amplifier incorporates dynamic supply voltage control where the stacked output stage receives different supply voltages depending on the power mode requirement. The driver stage maintains a fixed supply voltage to ensure stable operation, while the output stage voltage is dynamically adjusted to optimize efficiency across different power modes.
Solution Approach 2:
Different parts of the amplifier are given different supply voltage characteristics: the driver stage receives a fixed supply voltage for stable operation, while the stacked output stage receives a variable supply voltage that is optimized for each power mode. This local differentiation allows the system to achieve both adaptability and efficiency.
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
This configuration enhances power efficiency and maintains desirable operating characteristics across multiple power modes, preventing early power compression and reducing headroom issues, thus improving output power and efficiency in RF amplifiers.
Implementation Method 1
a driver stage including an injection-locked oscillator configured to generate an injection-locked radio frequency signal based on the radio frequency input signal
Implementation Method 2
a stacked output stage configured to amplify the injection-locked radio frequency signal to generate the output radio frequency signal
Data Source
AI summary
Radio frequency (RF) amplifiers, such as power amplifiers, are provided herein. In certain configurations, an RF amplifier includes an input terminal that receives an RF input signal, an output terminal that provides an RF output signal, an injection-locked oscillator driver stage that amplifies the RF input signal to generate an injection-locked RF signal, and a stacked output stage that further amplifies the injection-locked RF signal to generate the RF output signal. The stacked output stage includes a stack of at least a first transistor and a second transistor in series with one another. Thus, the stacked output stage is operable over a wide range of supply voltage to overcome the relatively low breakdown voltages of scaled transistors. Moreover, the injection-locked oscillator driver stage provides the RF amplifier with excellent power efficiency, including in applications in which the stacked output stage operates with a supply voltage that is variable.