Sensor Amplifier Feedback Circuit for Distortion-Free Dynamic Range
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Solution Overview
Problem
Existing sensor amplifier arrangements face issues with signal distortion and muting due to high sensor signal values, leading to reduced dynamic range and increased distortion for loud sounds, especially in capacitive sensors like MEMS microphones, where signal muting can occur for several seconds.
Innovation Solution
A sensor amplifier arrangement with a feedback path comprising an anti-parallel circuit of diodes, a feedback amplifier, an offset signal source, and a summing circuit that adjusts the gain based on the amplified sensor signal, providing a non-inverted amplified signal and controlling the feedback current in a non-linear fashion to reduce distortion and extend the dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional sensor amplifier arrangement is used, then the sensor signal is amplified, but signal distortion and muting occur when the sensor signal obtains high values
Solution Approach 1:
The patent implements a feedback path that couples the signal output back to the signal input through an anti-parallel diode circuit. This feedback mechanism dynamically adjusts the input impedance based on the sensor signal value, preventing signal distortion and muting by compensating for high signal values in real-time
Solution Approach 2:
The anti-parallel diode circuit in the feedback path creates a dynamic input impedance that adapts to the sensor signal amplitude. When the sensor signal is small, the input impedance remains high; when the sensor signal is large, the input impedance automatically decreases to prevent distortion, making the system behavior dynamic rather than static
2Measurement precision
If the input impedance is kept high for small sensor signal values, then noise levels are reduced, but the amplifier cannot handle high signal amplitudes without muting
Solution Approach 1:
The system employs dynamic impedance control through the feedback path with anti-parallel diodes. The input impedance transitions from high (for small signals) to low (for large signals) automatically, enabling the amplifier to maintain both low noise for small signals and high adaptability for large signals across the entire dynamic range
Solution Approach 2:
The input impedance parameter changes dynamically based on the sensor signal amplitude. The feedback mechanism modifies the effective input impedance to match the signal level, allowing the system to optimize both noise performance and dynamic range by adjusting this key parameter in response to operating conditions
3Adaptability or versatility
If a feedback path is added to reduce distortion, then the dynamic range is extended, but the device complexity increases
Solution Approach 1:
The feedback path uses a relatively simple anti-parallel diode circuit configuration to achieve dynamic range extension. By leveraging the non-linear characteristics of the anti-parallel diodes in a feedback topology, the system achieves complex adaptive behavior with a relatively simple additional circuit structure
Solution Approach 2:
The anti-parallel diode circuit acts as an intermediary element that mediates between the amplifier input and the feedback signal. This intermediary structure enables the complex function of dynamic impedance control and distortion reduction without requiring a completely complex circuit redesign
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
The solution effectively reduces signal distortion and extends the dynamic range of the sensor amplifier, allowing it to handle high signal amplitudes without muting, maintaining high input impedance and low noise levels, even for small sensor signal values.
Implementation Method 1
The feedback path couples the signal output to the signal input and comprises an anti-parallel circuit of diodes
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3B
AI summary
A sensor amplifier arrangement (10) includes an amplifier (11) having a signal input (12) to receive a sensor signal and a signal output (13) to provide an amplified sensor signal, and a feedback path (30) that couples the signal output (13) to the signal input (12) and provides a feedback current that is an attenuated signal of the amplified sensor signal and is inverted with respect to the sensor signal.