Nanopore Low-Noise Amplifier Feedback for Parasitic Capacitance
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Solution Overview
Problem
Nanopore-based molecular detection systems face challenges in reducing noise in ionic current measurements, which limits signal-to-noise ratio (SNR) and time resolution due to parasitic capacitance at the amplifier input, affecting the ability to detect small differences in ionic current as molecules translocate through nanopores.
Innovation Solution
The implementation of a feedback circuit that injects a charge into the sense electrode to cancel parasitic capacitance between the sense and counter electrodes, and the use of a bootstrap circuit to mitigate parasitic capacitance by providing a high-frequency voltage component, thereby reducing noise and improving SNR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard amplifier is used to detect ionic current, then the current can be amplified, but parasitic capacitance at the amplifier input causes noise peaking and SNR degradation
Solution Approach 1:
The patent implements a feedback circuit that senses the output signal from the amplifier and feeds back a compensating signal to the amplifier input. This feedback mechanism actively cancels the noise caused by parasitic capacitance, allowing the system to maintain high signal-to-noise ratio while using standard amplifiers with inherent input capacitance
Solution Approach 2:
The patent introduces an intermediary feedback circuit between the amplifier output and input. This intermediary circuit processes the output signal and generates a compensating signal that mediates the harmful effect of parasitic capacitance, converting the noise problem into a solvable signal processing task
2Speed
If the bandwidth is increased to improve time resolution, then faster molecular translocation can be detected, but noise increases due to capacitance
Solution Approach 1:
The feedback circuit operates across a broad frequency range to counteract capacitance effects at all relevant frequencies. By providing continuous feedback compensation, the system achieves high time resolution for fast molecular translocation events without suffering from capacitance-induced noise peaking that would normally limit bandwidth
3Object-affected harmful factors
If shielding is added to reduce parasitic capacitance, then noise is reduced, but device complexity increases
Solution Approach 1:
Rather than adding physical shielding structures that会增加 device complexity, the patent uses an electrical feedback solution. The feedback circuit electronically compensates for parasitic capacitance effects without requiring additional physical shields, ground planes, or structural modifications to the nanopore device
Solution Approach 2:
The patent replaces the mechanical/physical approach of adding shielding structures with an electrical/electronic feedback mechanism. Instead of physically blocking or reducing capacitance through shields and grounds, the system uses electrical feedback to cancel the capacitance effects, simplifying the device structure
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 amplifier input current noise, enhancing the SNR and time resolution of nanopore measurements, allowing for more accurate detection of molecular properties.
Implementation Method 1
the feedback circuit is coupled to the output of the amplifier and to the input of the amplifier, and the control logic is coupled to the feedback circuit and is configured to set at least one parameter of the feedback circuit to reduce a parasitic capacitance between the sense electrode and the counter electrode
Implementation Method 2
The capacitance at the input to the amplifier forms a pole with the output impedance of the amplifier. High capacitance at the input to the amplifier can cause noise peaking and SNR degradations.
Data Source
AI summary
Disclosed herein are devices, systems, and methods that can improve the SNR of nanopore measurements by mitigating the effect of parasitic capacitance between the sense electrode and the counter electrode. In some embodiments, a feedback circuit is used to inject a charge into the sense electrode to at least partially cancel the parasitic capacitance between the sense electrode and the counter electrode. In some embodiments, bootstrapping of a signal from the amplifier output or from the sense electrode is used to inject a charge on the counter electrode to substantially cancel the parasitic capacitance.