Nanopore Amplifier Feedback to Cancel Parasitic Capacitance
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Solution Overview
Problem
Nanopore-based systems face challenges in detecting molecules due to noise in ionic current measurements, primarily caused by parasitic capacitance at the amplifier input, which limits signal-to-noise ratio and time resolution.
Innovation Solution
A system incorporating a feedback circuit that injects a charge into the sense electrode to cancel parasitic capacitance between the sense and counter electrodes, along with a bootstrap circuit that provides a high-frequency voltage to mitigate capacitance effects, improving signal quality and reducing noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a standard amplifier is used to detect ionic current through the nanopore, then the current can be amplified and measured, but the parasitic capacitance at the amplifier input causes noise peaking and signal-to-noise ratio degradation
Solution Approach 1:
The patent applies feedback by connecting a feedback capacitor between the output and input of the amplifier. This feedback mechanism compensates for the parasitic capacitance at the amplifier input by injecting a compensating charge that cancels out the noise-generating effect of the parasitic capacitance, thereby improving the signal-to-noise ratio without requiring changes to the amplifier's fundamental operation
Solution Approach 2:
The patent changes the effective capacitance parameter at the amplifier input by introducing a controllable feedback capacitor. By adjusting the feedback capacitor's value and characteristics, the system optimizes the total input capacitance to minimize noise peaking while maintaining the necessary signal amplification, thus resolving the contradiction between measurement precision and harmful noise effects
2Speed
If the bandwidth of the amplifier is increased to improve temporal resolution, then faster molecular translocation can be detected, but the noise level increases due to the amplified bandwidth
Solution Approach 1:
The feedback capacitor provides frequency-dependent compensation that is particularly effective at higher frequencies where temporal resolution is critical. By maintaining proper compensation across the bandwidth, the system can operate at higher speeds without the noise penalty that would normally accompany increased bandwidth
Solution Approach 2:
The system dynamically manages the effective input capacitance parameter across different frequency ranges, allowing the amplifier to maintain low noise performance even when operating with increased bandwidth for improved temporal resolution
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 significantly reduces amplifier input current noise, enhancing the signal-to-noise ratio and allowing for more accurate and rapid detection of molecules passing through the nanopore.
Implementation Method 1
parasitic capacitance between the sense electrode and the counter electrode
Implementation Method 2
capacitance at the input to the amplifier forms a pole with the output impedance of the amplifier
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.