Cryogenic Current-Voltage Converter With Multi-Stage Feedback
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Solution Overview
Problem
Existing current-voltage conversion devices used for measuring minute currents in cryogenic environments suffer from noise generation and variation in band characteristics due to element variation.
Innovation Solution
A current-voltage conversion device with an amplification unit comprising at least three stages of electronic elements, a buffer unit for outputting the converted voltage, and a configuration that includes a common first voltage for all electronic elements and a second voltage for the first-stage element, along with multiple feedback circuits connected in series to reduce noise and enhance bandwidth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional current-voltage conversion device is used for measuring minute currents in cryogenic environments, then the device can perform basic current measurement, but noise is generated and band characteristics vary due to element variation
Solution Approach 1:
The amplification unit is divided into multiple stages (first-stage amplification unit, second-stage amplification unit, etc.), where each stage contributes to the overall gain. This segmentation allows for optimized noise performance at each stage while achieving the required total amplification, resolving the contradiction between measurement precision and noise by distributing the amplification function across multiple controlled stages
Solution Approach 2:
Different voltage supplies are applied to different parts of the circuit: a first voltage supply is used for the first-stage amplification unit to optimize its noise characteristics, while a second voltage supply is used for subsequent stages. This local differentiation of operating conditions allows each stage to be optimized for its specific function, improving overall measurement precision while controlling noise
2Speed
If a conventional current-voltage conversion device is used for measuring minute currents in cryogenic environments, then the device can perform basic current measurement, but band characteristics vary due to element variation
Solution Approach 1:
Feedback circuits are incorporated in the amplification stages to stabilize the band characteristics. The feedback mechanism compensates for variations in active元件 parameters, ensuring consistent bandwidth performance across different devices and operating conditions, thus resolving the contradiction between speed (bandwidth) and reliability (characteristic variation)
Solution Approach 2:
Multiple voltage supplies are used to independently control the operating parameters of different amplification stages. By adjusting the voltage levels, the bandwidth and other characteristics can be optimized and stabilized, reducing variation due to element parameters while maintaining the required speed performance
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 device achieves highly sensitive and broadband measurement of minute currents, significantly reducing noise and improving time resolution in cryogenic environments.
Implementation Method 1
each of the plurality of feedback circuits includes a resistive element
Data Source
AI summary
A current-voltage conversion device that operates with low noise and a wide band is disclosed. In addition to a power supply terminal for supplying a common power supply voltage to five HEMTs (H1 to H5), a dedicated second power supply terminal for the first-stage source common circuit of the first-stage HEMT (H1) is provided. Feedback from H4 to H1 in a current-voltage conversion unit includes a feedback circuit including a plurality of resistive elements connected in series. The feedback circuit is configured by parallel connection of a feedback resistive element having a resistance value RFBk and a feedback capacitor having a capacitance value CFBk (k=1, 2, 3, . . . n). A small feedback capacitance CFB of 1 pF or less is realized using a parasitic capacitance of a resistive element as a necessary capacitance in a feedback circuit. The time resolution of a current-voltage conversion device is enhanced.