Transimpedance Amplifier Module for High-Precision Current Measurement

Solution Overview

Problem

Current measurement apparatuses for base sequence analysis, such as nanopore sequencing, face challenges in achieving high-precision current measurement due to noise interference, particularly when dealing with tunnel currents in the order of several tens of picoamperes and conductance differences in the picosecond range.

Innovation Solution

A measurement apparatus is designed with a transimpedance amplifier built into a first module positioned near the device under test, along with guard metal members and voltage sources, to reduce noise effects and input capacitance, enabling high-precision and wide-bandwidth current measurement by converting current signals to voltage signals locally and controlling electric potentials to minimize parasitic capacitance and noise.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If the transimpedance amplifier is positioned far from the device under test, then the digital circuit noise can be isolated, but the input capacitance increases and measurement bandwidth decreases

Engineering Contradiction:

Improvecurrent measurement precisionVSAvoidmodule separation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The measurement apparatus is divided into two separate modules: a first module containing the transimpedance amplifier positioned near the device under test, and a second module containing the digital circuit. This segmentation allows the sensitive analog measurement function to be isolated from digital noise sources while maintaining close proximity to the device under test, thus resolving the contradiction between noise isolation and measurement bandwidth.

Inventive Principle:

Principle #1Segmentation

2Speed

If the transimpedance amplifier is positioned near the device under test, then the input capacitance is reduced and bandwidth is increased, but noise from the digital circuit may interfere with the measurement

Engineering Contradiction:

Improvemeasurement bandwidthVSAvoiddigital circuit noise

Core Design Contradiction:

SpeedVSObject-affected harmful factors

Solution Approach 1:

The measurement apparatus is divided into two separate modules: a first module containing the transimpedance amplifier positioned near the device under test, and a second module containing the digital circuit. This segmentation allows the sensitive analog measurement function to be isolated from digital noise sources while maintaining close proximity to the device under test, thus resolving the contradiction between noise isolation and measurement bandwidth.

Inventive Principle:

Principle #1Segmentation

3Device complexity

If a single integrated module is used, then the device structure is simplified, but noise interference from digital circuits increases and measurement precision decreases

Engineering Contradiction:

Improvemodule structure simplicityVSAvoidtunnel current measurement precision

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The measurement apparatus is divided into two separate modules: a first module containing the transimpedance amplifier positioned near the device under test, and a second module containing the digital circuit. This segmentation allows the sensitive analog measurement function to be isolated from digital noise sources while maintaining close proximity to the device under test, thus resolving the contradiction between noise isolation and measurement bandwidth.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A cable connects the first module (with transimpedance amplifier) to the second module (with digital circuit), serving as an intermediary that transmits the measured signal while isolating the sensitive analog circuitry from digital noise sources. This intermediary connection allows the system to benefit from both modular isolation and integrated functionality.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 noise interference, allowing for precise measurement of tunnel currents and improving the accuracy of base sequence analysis by minimizing noise components in the current and voltage signals, thereby enhancing the measurement precision and bandwidth.

Implementation Method 1

a transimpedance amplifier that converts the current signal into a voltage signal

Methodology Applied

Scientific EffectTransimpedance conversion:

Implementation Method 2

a digitizer that converts the voltage signal into first digital data

Methodology Applied

Scientific EffectAnalog-to-digital conversion:

Implementation Method 3

a guard amplifier that is built into the first module, and that applies a virtual ground voltage of the transimpedance amplifier to the guard metal member

Methodology Applied

Scientific EffectVirtual ground:

Data Source

PatentUS10228362B2Measurement apparatus

Publication Date: 2019.03.12 ADVANTEST CORP

AI summary

A measurement apparatus is provided that measures a current signal IDUT that flows through a device under test. A transimpedance amplifier converts the current signal IDUT into a voltage signal VOUT. A digitizer converts the voltage signal VOUT into first digital data. A digital signal processing unit performs signal processing on the first digital data, and controls the measurement apparatus. The measurement apparatus has a configuration comprising two separate modules, i.e., a probe module which is located in the vicinity of the device under test during a measurement, and a backend module connected to the probe module via at least one cable. The transimpedance amplifier is built into the probe module.