Low-Noise Amplifier Gain Steps Using Bypass and Current Steering
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Solution Overview
Problem
Existing low noise amplifiers (LNAs) face challenges in achieving multiple gain steps while maintaining low noise figure and good output linearity, especially across different power modes.
Innovation Solution
The proposed LNA design includes an amplifier chain with multiple differential amplification stages operable in various power modes, featuring a bypass switch network and current steering for gain control, allowing for efficient gain tuning and minimal impact on port impedances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple gain steps are implemented in existing LNAs, then gain control is improved, but noise figure and output linearity deteriorate
Solution Approach 1:
The amplifier chain is divided into multiple differential amplification stages (first, second, and third stages) that can be independently controlled. Each stage can be selectively enabled or bypassed to achieve different gain steps, allowing gain control while maintaining optimal noise figure and linearity characteristics for each operational mode.
Solution Approach 2:
The LNA implements dynamic reconfiguration through bypass switch networks that can rapidly switch between different amplification paths. The bypass switches enable or disable specific amplification stages based on the desired gain level, allowing the system to adapt its characteristics dynamically while maintaining low noise figure and good output linearity across all gain steps.
2Adaptability or versatility
If amplification stages are added to achieve multiple gain steps, then gain control is improved, but device complexity increases
Solution Approach 1:
Each differential amplification stage is designed to provide both amplification and impedance transformation functions. The bypass switches serve dual purposes by either connecting the signal through an amplification stage or bypassing it entirely. This multi-functionality reduces the need for separate dedicated components for each function, thereby managing device complexity while achieving multiple gain steps.
3Adaptability or versatility
If bypass switches are used to achieve gain steps, then gain control is improved, but impact on port impedances increases
Solution Approach 1:
The differential amplification stages are designed with local impedance matching networks that ensure proper impedance transformation regardless of which stages are active. Each stage is optimized to maintain specific impedance characteristics at its input and output ports, ensuring that the overall port impedances remain stable across different gain configurations. This localized optimization compensates for the impedance variations that would otherwise be introduced by the bypass switches.
Data Source
AI summary
Low noise amplifiers (LNAs) are disclosed herein. In certain embodiments, an LNA includes an input balun configured to convert a single-ended radio frequency (RF) receive signal to a differential RF receive signal, an amplifier chain configured to amplify the differential RF receive signal to generate a differential amplified RF receive signal, and an output balun configured to convert the differential amplified RF receive signal into a single-ended amplified RF receive signal. The LNA's amplifier chain is operable in multiple gain modes, and includes a first differential amplification stage, a second differential amplification stage, and a third differential amplification stage.