Current Mirror LNA Biasing for Wide Gain Stability
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Solution Overview
Problem
Conventional low-noise RF amplifiers operating in the variable-gain mode require high supply voltages and high power consumption, limiting their applicability in low-voltage nanometer technology and making it challenging to achieve wide gain range variations with high linearity and low noise figures without stability issues.
Innovation Solution
The proposed solution involves a single-stage low-noise amplifier design using a current mirror approach and a DC output closed loop, which facilitates high-linearity, low-noise figure performance across a wide gain range without the need for a stability network, and is suitable for implementation in low-voltage, high-performance advanced CMOS technology, including a high-impedance buffer to enhance gain and reduce oscillations and spurious signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If conventional low-noise RF amplifiers are designed to operate with wide gain range variations, then gain adaptability is improved, but power consumption increases and stability deteriorates
Solution Approach 1:
The amplifier is divided into multiple stages with independent gain control. Each stage contributes to the overall gain range, allowing wide gain variation (e.g., 0-60 dB) while maintaining efficient power consumption. The first stage operates at low power with the second stage providing additional gain when needed, rather than requiring the entire amplifier to operate at high power levels continuously.
Solution Approach 2:
The amplifier employs dynamic gain control through variable gain amplifiers (VGAs) in each stage. The gain of each stage can be independently adjusted based on signal requirements, enabling the system to adapt to different operating conditions and minimize power consumption while maintaining the required gain range.
2Reliability
If conventional amplifiers use high supply voltage to achieve high linearity, then linearity is improved, but power consumption increases and device compatibility worsens
Solution Approach 1:
The amplifier is segmented into multiple stages, each contributing to the overall linearity performance. This allows the system to achieve high linearity through the cumulative effect of multiple low-voltage stages rather than requiring a single high-voltage stage, thereby reducing power consumption while maintaining reliability.
Solution Approach 2:
The invention changes the operating parameters of each amplifier stage to optimize the trade-off between linearity and power consumption. By carefully selecting bias conditions, impedance levels, and gain settings for each stage, the system achieves high overall linearity while operating at lower supply voltages and reduced power consumption.
3Adaptability or versatility
If conventional amplifiers operate with wide gain range, then adaptability is improved, but stability deteriorates due to oscillation and spurious signals
Solution Approach 1:
The amplifier is divided into multiple stages, each with controlled gain and bandwidth characteristics. This segmentation prevents any single stage from operating in unstable conditions that could cause oscillation, while the cumulative gain across stages achieves the desired wide gain range. Each stage can be independently stabilized, improving overall system stability.
Solution Approach 2:
The invention employs feedback mechanisms in each amplifier stage to maintain stability across the wide gain range. By monitoring output signals and adjusting stage parameters accordingly, the system prevents oscillation and spurious signals while maintaining adaptability. The feedback ensures that each stage operates within stable boundaries regardless of the overall gain setting.
Data Source
AI summary
A circuit an amplifier stage that amplifier stage includes a positive amplifier branch and a negative amplifier branch and has current flow paths therethrough cascaded in a flow line for a core current for the amplifier stage between a supply node and a ground node. The positive and negative amplifier branches have respective input nodes configured to receive an input signal applied therebetween. A current mirror loop can be coupled to the respective input nodes of the positive and negative amplifier branches and provides an adjustable high-impedance bias source for the core current for the amplifier stage. In addition to, or instead of the current mirror loop, the circuit can include stability network having a gain bandwidth range. The amplifier stage is configured to short-circuit the output signal from the amplifier stage within the gain bandwidth range based on an output voltage setting signal.