Chopper-Stabilized Baseband Amplifier for 1/f Noise Reduction
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Solution Overview
Problem
Low-frequency CMOS amplifiers suffer from 1/f noise, which is not effectively reduced in existing baseband filters.
Innovation Solution
The implementation of chopper-stabilized amplifiers, which modulate input signals with a high-frequency chopping signal and use a low-pass filter to eliminate 1/f noise by up-converting it to the chopping frequency, where it is filtered out.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-frequency CMOS amplifiers are used in baseband filters, then device complexity is reduced and ease of manufacture is improved, but 1/f noise increases significantly
Solution Approach 1:
The patent applies periodic chopping signals to modulate the amplifier operation. The chopper circuit periodically switches the amplifier on and off at a high frequency, which modulates the 1/f noise to a higher frequency band where it can be filtered out, thereby reducing the noise in the baseband while maintaining the benefits of low-frequency CMOS amplifiers
Solution Approach 2:
The patent introduces chopper circuits as intermediary elements between the input signal and the amplifier, and between the amplifier output and the baseband filter. These intermediary chopper circuits modulate the signal and noise frequencies, allowing the harmful 1/f noise to be separated from the baseband signal and removed by filtering
2Object-generated harmful factors
If chopper-stabilized amplifiers are used to reduce 1/f noise, then noise performance is improved, but device complexity increases due to additional chopper circuits
Solution Approach 1:
The patent divides the noise reduction function into separate chopper circuit modules that can be independently implemented. By segmenting the baseband filter into multiple stages with individual chopper-stabilized amplifier sections, the complexity is distributed and managed more effectively rather than requiring a single complex noise-reduction mechanism
3Object-generated harmful factors
If chopping frequency is increased to better filter 1/f noise, then noise reduction effectiveness is improved, but interference with signal spectrum may increase
Solution Approach 1:
The patent employs dynamic adjustment of the chopping frequency based on the signal characteristics and filter requirements. The chopping frequency can be adaptively tuned to optimize the separation between the modulated noise and the baseband signal, ensuring effective noise reduction while avoiding interference with the signal spectrum
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces 1/f noise in baseband filters by using chopper-stabilized amplifiers and low-pass filtering, improving noise performance in CMOS amplifiers.
Implementation Method 1
a first chopper circuit receiving an input signal and a chopping signal having a frequency higher than a base band of the input signal, and providing a modulated input signal
Implementation Method 2
a low pass filter that receives the output signal and that attenuates components of the output signal above the base band of the input signal. In this manner 1/f noise introduced by the amplifier is eliminated or reduced
Data Source
AI summary
An active circuit includes (a) a first chopper circuit that receives an input signal and a chopping signal of a frequency higher than a base band of the input signal, and that provides a modulated input signal; (b) an amplifier that receives the modulated input signal and that provides an amplified signal resulting from amplifying the modulated input signal; and (c) a second chopper circuit that receives the amplified signal and the chopping signal to provide an output signal. The chopping signal has a frequency that may be dynamically adjusted to accommodate changes in impedance and signal spectrum as a result of the operations of the chopper circuits. The active circuit further includes a low pass filter that receives the output signal and that attenuates components of the output signal above the base band of the input signal. In this manner 1/f noise introduced by the amplifier is eliminated or reduced.