Stacked Multi-Stage LNA Bias Sharing for Lower Wideband Power
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Solution Overview
Problem
Existing low noise amplifiers (LNAs) face a tradeoff between wideband performance and power consumption, with increased power usage often required for improved wideband operation, which is undesirable in portable applications where battery longevity is a concern.
Innovation Solution
A multi-stage LNA configuration with a common DC current conduction path is introduced, allowing both stages to operate from the same bias current and incorporating a current splitter circuit to manage DC current distribution, thereby reducing power consumption while maintaining wideband performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a multi-stage LNA configuration is used to improve wideband performance, then bandwidth and performance are improved, but power consumption increases
Solution Approach 1:
The LNA is divided into multiple stages with distinct functions: a first stage for low-frequency operation and a second stage for high-frequency operation. This segmentation allows each stage to be optimized for specific frequency ranges, improving overall wideband performance while enabling selective activation to reduce power consumption.
Solution Approach 2:
The patent implements dynamic switching between different stages based on the operating frequency. A switching mechanism selectively activates the first stage for low-frequency signals and the second stage for high-frequency signals, allowing the system to adapt its power consumption to the actual operating conditions rather than continuously powering all stages.
2Reliability
If separate bias currents are used for each stage to optimize individual performance, then stage-specific performance is improved, but device complexity and power management increase
Solution Approach 1:
A single bias current source is designed to serve multiple functions: it provides bias current to both the first stage and the second stage, and also generates the control signal for the switching mechanism. This multi-functionality reduces the number of separate bias circuits needed, simplifying the overall device complexity while maintaining the ability to optimize each stage's performance.
Solution Approach 2:
The patent combines the bias current generation and switching control functions into a single integrated bias current source. By merging these functions, the patent reduces the number of separate components and simplifies the power management architecture, making the system easier to implement and control.
Data Source
AI summary
Methods and devices for reducing DC current consumption of a multi-stage LNA amplifier. According to one aspect, first and second amplification stages are stacked to provide a common conduction path of a DC current. The first stage includes a common-source amplifier, the second stage includes a common-drain amplifier. Coupling between the two stages is provided by series connection of load inductors of the respective stages and a capacitor coupled at a common node between the inductors. According to another aspect, a current splitter circuit is used to split a current to the first stage according to two separate conduction paths, one common path to the two stages, and another separate from the second stage. According to yet another aspect, the current splitter circuit includes a feedback loop that controls the splitting of the current so to maintain a constant current through the common path.