Split Cascode LNA Switching for High-Voltage OFF-State Protection
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Solution Overview
Problem
Existing low noise amplifier (LNA) designs face issues with high voltages across output transistors when turned OFF, potentially leading to time-dependent dielectric breakdown, which can degrade receiver performance and require thicker gate oxide layers, increasing noise figure and reducing third-order intercept point.
Innovation Solution
The design incorporates a source switch to connect the source terminals of LNA branches, allowing for operation in single and split modes, with amplifier-branch control switches using thick gate oxide layers to manage power supply voltages, enabling the use of thinner gate oxide layers in output transistors for improved noise figure and third-order intercept performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If thick gate oxide layers are used in output transistors to withstand high OFF-state voltages, then reliability is improved, but noise figure increases and third-order intercept point decreases
Solution Approach 1:
The patent divides the LNA into multiple branches with separate output transistors, each handling specific voltage conditions. By segmenting the amplifier structure, the design can apply different gate oxide thicknesses to different transistor branches, allowing thin-oxide transistors to handle low-voltage signals while thick-oxide transistors handle high-voltage switch operations, thereby resolving the contradiction between reliability and noise performance
Solution Approach 2:
The patent implements local quality by using thin gate oxide layers specifically in the signal path transistors where low noise is critical, while using thick gate oxide layers in switch transistors where voltage withstanding is critical. This localized differentiation allows each part of the circuit to have optimal properties for its specific function, resolving the contradiction between reliability and noise figure
2Reliability
If thick gate oxide layers are used in output transistors to withstand high OFF-state voltages, then reliability is improved, but third-order intercept point decreases
Solution Approach 1:
The patent segments the LNA into multiple branches with separate output transistors, allowing thin-oxide transistors to handle low-voltage signals for optimal linearity while thick-oxide transistors handle high-voltage switch operations, resolving the contradiction between reliability and third-order intercept point
Solution Approach 2:
The patent applies local quality by using thin gate oxide layers in signal path transistors where high third-order intercept point is critical for linearity, while using thick gate oxide layers in switch transistors where voltage withstanding is critical, thereby resolving the contradiction between reliability and third-order intercept point
3Adaptability or versatility
If multiple LNA branches are used to handle different frequency ranges, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing LNA branches that can operate in both single-mode and split-mode configurations. The same physical hardware can handle different frequency ranges and operating modes, providing adaptability without proportionally increasing complexity. The circuit can dynamically reconfigure itself based on the input signal characteristics
Solution Approach 2:
The patent applies dynamics by enabling the LNA to dynamically switch between single-mode and split-mode operation. The circuit can adapt its configuration in real-time based on the frequency and characteristics of the input signal, allowing a single device to provide multiple functions across different frequency ranges without requiring separate fixed circuits for each mode
Data Source
AI summary
A receiver front end capable of receiving and processing intraband non-contiguous carrier aggregate (CA) signals using multiple low noise amplifiers (LNAs). Cascode circuits, each having a “common source” configured input FET and a “common gate” configured output FET, serve as the LNAs. An amplifier-branch control switch, configured to withstand relatively high voltage differentials by means of a relatively thick gate oxide layer and coupled between a terminal of the output FET and a power supply, controls the ON and OFF state of each LNA while enabling use of a relatively thin gate oxide layer for the output FETs, thus improving LNA performance. Some embodiments may include a split cascode amplifier and/or a power amplifier.