High-Ohmic Resistor Parasitic Pole Zero Compensation
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Solution Overview
Problem
MEMS capacitive sensors, such as MEMS microphones, face noise issues due to parasitic capacitances in high-ohmic bias resistors, which affect the signal-to-noise ratio (SNR) by introducing parasitic poles and zeros in the noise transfer function, leading to increased noise and reduced performance.
Innovation Solution
Incorporating a high-Ω resistor design with semiconductor junction devices connected in series and additional parasitic capacitances in parallel, where each semiconductor junction device includes a parasitic doped well capacitance to introduce a parasitic zero, and additional capacitances are used to compensate for this zero by adjusting the parasitic pole, thereby improving the SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a high-ohmic bias resistor is used in MEMS capacitive sensors, then the biasing function is achieved, but parasitic capacitances introduce poles and zeros in the noise transfer function, increasing noise and reducing signal-to-noise ratio
Solution Approach 1:
The patent converts the harmful parasitic capacitances into beneficial elements by intentionally adding compensation capacitances that utilize the same parasitic effects to create zeros in the noise transfer function, thereby canceling the harmful poles and improving the signal-to-noise ratio
Solution Approach 2:
The patent modifies the electrical parameters of the bias resistor circuit by adding specific capacitance values to compensate for parasitic effects, changing the pole-zero distribution in the noise transfer function to achieve lower noise performance
2Reliability
If additional capacitances are added to compensate for parasitic zeros, then noise is reduced and SNR is improved, but device complexity increases
Solution Approach 1:
The patent merges the compensation capacitances with existing circuit elements or integrates them directly into the bias resistor structure, thereby reducing the number of discrete components and minimizing the increase in device complexity while achieving noise reduction
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 configuration reduces noise and enhances the signal-to-noise ratio by effectively managing parasitic influences, leading to improved performance and larger signal swings in MEMS capacitive sensing systems.
Implementation Method 1
Each semiconductor junction device of the plurality of semiconductor junction devices includes a parasitic doped well capacitance configured to insert a parasitic zero in a noise transfer function of the high-Ω resistor
Implementation Method 2
Each additional capacitance of the plurality of additional capacitances is configured to adjust a parasitic pole in the noise transfer function of the high-Ω resistor in order to compensate for the parasitic zero
Data Source
AI summary
According to an embodiment, a circuit includes a high-Ω resistor including a plurality of semiconductor junction devices coupled in series and a plurality of additional capacitances formed in parallel with the plurality of semiconductor junction devices. Each semiconductor junction device of the plurality of semiconductor junction devices includes a parasitic doped well capacitance configured to insert a parasitic zero in a noise transfer function of the high-Ω resistor. Each additional capacitance of the plurality of additional capacitances is configured to adjust a parasitic pole in the noise transfer function of the high-Ω resistor in order to compensate for the parasitic zero.