Microphone Preamplifier Feedback Circuit for Higher SNR
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Solution Overview
Problem
Existing microphone amplifier circuits, particularly those using digital MEMS microphone modules, face challenges in enhancing the signal-to-noise ratio (SNR) and expanding dynamic range, with noise sources primarily located at the preamplifier stage, necessitating a cost- and time-efficient solution.
Innovation Solution
The proposed solution involves a preamplifier circuit configuration that includes a filter connected to a comparator with a feedback loop, where the output of the amplifier is filtered and compared to a reference voltage, with the feedback signal adjusting the voltage to be equal to half the supply voltage difference, thereby optimizing the dynamic range and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional preamplifier stage is used in digital MEMS microphone modules, then the basic amplification function is achieved, but the signal-to-noise ratio deteriorates due to noise generated at the preamplifier stage
Solution Approach 1:
The patent extracts and removes the noise-generating components from the preamplifier stage by implementing a capacitor-based amplification approach that eliminates the need for traditional noisy amplifiers, thereby removing the harmful noise source while preserving the amplification function
Solution Approach 2:
The patent introduces capacitors as intermediary elements to perform the amplification function traditionally handled by noisy active components. The capacitors serve as noise-free mediators that enable signal amplification through charge redistribution rather than active device multiplication
2Adaptability or versatility
If the dynamic range of the microphone amplifier circuit is expanded, then the quality of electrical signals is improved, but the circuit complexity and cost increase
Solution Approach 1:
The patent achieves expanded dynamic range by changing the operational parameters of the capacitor-based amplification circuit, specifically utilizing different capacitance values and charge redistribution ratios to achieve variable gain stages, thereby expanding dynamic range through parameter optimization rather than additional circuit stages
Solution Approach 2:
The patent implements a multi-functional capacitor network that simultaneously performs amplification, dynamic range control, and noise filtering functions within a single integrated stage, eliminating the need for separate circuit blocks and reducing overall circuit complexity while achieving expanded dynamic range
Data Source
AI summary
In accordance with an embodiment, method for generating an output signal of an amplifier having an increased signal to noise ratio includes receiving a first signal at an input terminal of the amplifier that is not part of a differential input. The input terminal of the amplifier is a sole input terminal of the amplifier. The first signal has an externally received portion and a feedback portion. A first amplified signal is generated at an output of the amplifier. High frequency components of the first amplified signal may be filtered. A feedback signal is generated at the sole input terminal of the amplifier in response to the first output signal.