Current-Mode Noise Cancellation Circuit for Low-Power LNAs
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Solution Overview
Problem
Conventional noise cancellation techniques for low-noise amplifiers face challenges in scalability, linearity, noise figure, chip area, and current consumption, particularly in low-power applications, and fail to effectively address flicker noise without compromising current or transistor size.
Innovation Solution
A signal processing circuit with circuit-induced noise cancellation is proposed, incorporating an impedance matching unit and a transconductance stage for noise cancellation, utilizing passive elements and voltage-to-current converting units to combine current signals for effective noise cancellation without compromising current consumption or noise performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If inductor degeneration design is employed for impedance and noise matching, then noise performance is improved, but chip area consumption increases
Solution Approach 1:
The patent extracts the noise matching function from the traditional inductor degeneration topology and implements it through a separate noise cancellation circuit that uses transistors and resistors instead of large inductors, thereby achieving the same noise performance without the area penalty of inductor-based designs
Solution Approach 2:
The patent introduces an intermediary noise cancellation circuit that includes a first transistor connected in parallel with the input terminal and a second transistor connected to the drain of the first transistor. This intermediary circuit mediates between the input signal and the amplifier core, providing noise matching through the transistors rather than through large inductors
2Reliability
If conventional noise cancellation techniques are used to provide wide-band matching and lower noise figure, then noise performance is improved, but current consumption increases
Solution Approach 1:
The patent changes the operating parameters of the noise cancellation circuit by using resistors with specific resistance values (e.g., 1/k times the source resistance) and transistors with specific transconductance values to achieve noise cancellation with optimized current consumption, rather than using conventional techniques that require higher currents
3Object-generated harmful factors
If conventional noise cancellation technique is applied to deal with flicker noise, then flicker noise is reduced, but transistor size or current consumption increases
Solution Approach 1:
The patent extracts the flicker noise cancellation function from the main amplifier path and implements it through a dedicated noise cancellation circuit that uses a second transistor specifically configured to cancel flicker noise, allowing the main amplifier transistors to be smaller without sacrificing noise performance
Solution Approach 2:
The patent introduces a second transistor as an intermediary element that is specifically dedicated to flicker noise cancellation. This second transistor is connected to the drain of the first transistor and provides flicker noise cancellation without requiring the main amplifier transistors to be oversized
4Reliability
If conventional noise cancellation techniques are used, then noise cancellation is achieved, but the design is not current scalable for different applications
Solution Approach 1:
The patent creates a universal noise cancellation circuit topology that can be adapted to different current requirements and application scenarios. The circuit uses proportional relationships between resistor values and transconductance values that can be scaled while maintaining the noise cancellation function, making it applicable from low-power to high-performance applications
Data Source
AI summary
A signal processing circuit with noise cancellation includes an impedance matching unit and a transconductance stage. The impedance matching unit is disposed at a first path, and arranged to provide input impedance matching, wherein the impedance matching unit is a passive element, and the first path is coupled between a signal input port and a signal output port. The transconductance stage is disposed at a second path, and arranged to guide circuit introduced noise to the signal output port for noise cancellation at the signal output port, wherein the second path is coupled between the signal input port and the signal output port.