Potential Measurement Circuit for 1-300 Hz Low-Noise Signal Capture
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Solution Overview
Problem
Existing potential measuring devices struggle to simultaneously acquire signals of both action potentials (AP) and local field potentials (LFP) due to limitations in frequency range, particularly failing to capture LFP signals below 100 Hz because of leakage currents in sample-and-hold capacitors, which require frequent auto-zero operations.
Innovation Solution
A potential measuring device utilizing a common-source amplifier with a high resistance element and a buffer circuit, allowing for the acquisition of signals in the frequency range of 1 Hz to 300 Hz by maintaining a constant reference potential through a high resistance element, separate from the common readout signal line, and employing a stacked substrate configuration to enhance resolution and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sample-and-hold capacitor is used to hold reference potential in the reference cell, then the reference potential can be maintained, but leakage current causes operating point shifts and prevents acquisition of signals below 100 Hz
Solution Approach 1:
The patent extracts the problematic sample-and-hold capacitor from the reference cell configuration. By removing this component that causes leakage current and operating point shifts, the system can maintain reference potential stability through alternative means (such as direct connection to ground or use of a different reference generation method) while enabling acquisition of low-frequency signals down to 1 Hz without the 100 Hz lower limit constraint.
Solution Approach 2:
The patent addresses the harmful effect of leakage current in sample-and-hold capacitors by eliminating the need for auto-zero operations. By removing the source of leakage current, the system converts the harmful periodic refresh requirement into a continuous low-frequency signal acquisition capability, allowing LFP signals in the 1-300 Hz range to be captured without interference from capacitor discharge cycles.
2Measurement precision
If high sampling rate and high resolution are achieved through dense electrode arrangement, then action potential measurement is improved, but low-frequency signal acquisition is compromised
Solution Approach 1:
The patent implements a universal measurement system that can simultaneously acquire both high-frequency action potentials (AP) and low-frequency local field potentials (LFP). By removing the frequency limitation imposed by sample-and-hold capacitors and implementing a continuous reference potential system, the same electrode array and amplifier circuitry can capture signals across the entire 1 Hz to 10 kHz frequency range without requiring separate measurement systems.
3Reliability
If auto-zero operation is performed at regular intervals to refresh reference potential, then reference stability is maintained, but signals below the auto-zero frequency cannot be acquired
Solution Approach 1:
The patent removes the auto-zero operation mechanism from the system by eliminating the sample-and-hold capacitor that requires periodic refreshing. Instead, the reference potential is maintained continuously through alternative circuitry that does not require periodic discharge and recharge cycles, thereby enabling accurate acquisition of signals at frequencies below the auto-zero refresh rate.
Data Source
AI summary
The present technology relates to a potential measuring device capable of acquiring a signal of low-frequency bands of approximately 1 Hz to 300 Hz. The potential measuring device includes: a unit cell that includes a readout electrode for reading a predetermined potential as a displacement with respect to a reference potential, an amplifier circuit that includes a common-source amplifier, the readout electrode being connected to an input node of the common-source amplifier, a predetermined bias voltage being applied to the input node via a resistor, and a buffer circuit that is connected to an output node of the amplifier circuit. The present technology is applicable to, for example, a device for measuring the potential of a solution on a microelectrode.