Dosimeter Using Complementary MOSFETs for Radiation Sensitivity
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Solution Overview
Problem
Conventional dosimeters, such as Geiger counters and RADFETs, are limited by high costs, large size, and reduced sensitivity in detecting ionizing radiation, requiring complex circuitry and amplification that is not fully effective due to small output changes and large starting voltages.
Innovation Solution
A dosimeter utilizing a pair of transistors with different conductivity types (n-doped and p-doped MOSFETs) that generate outputs shifting in opposite directions in response to radiation, with a circuit to amplify the difference between these outputs, and optional resistive and temperature-sensitive elements for enhanced sensitivity and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If RADFET output is amplified to improve measurement sensitivity, then the measurement precision improves, but the output is limited by supply voltage and the amplification of large starting voltage reduces the effective amplification of radiation-induced changes
Solution Approach 1:
The patent divides the single RADFET measurement into two separate transistor measurements (first and second transistors with different conductivity types). Each transistor processes a portion of the radiation signal independently, allowing the differences between their outputs to be amplified without being constrained by the large starting voltage of a single transistor. This segmentation enables more effective amplification of the radiation-induced changes.
Solution Approach 2:
The patent uses transistors with different conductivity types (n-type and p-type) to create locally differentiated responses. The first transistor with first conductivity type and the second transistor with second conductivity type respond differently to radiation, creating a differential signal that enhances measurement sensitivity while reducing the impact of large starting voltages on the amplification process.
2Reliability
If conventional dosimeters are used to detect radiation, then radiation detection is achieved, but the device size and cost increase
Solution Approach 1:
The patent combines two transistors with different conductivity types into a single integrated dosimeter structure. By merging the functions of radiation detection and differential signal processing into one compact unit, the patent achieves reliable radiation detection while minimizing device size compared to conventional separate components like Geiger counters.
Solution Approach 2:
The dosimeter circuit performs multiple functions within a single device: radiation detection, differential signal generation, and amplification. The first and second transistors serve dual purposes as both radiation-sensitive elements and signal processing components, eliminating the need for separate detection and measurement circuits and thereby reducing overall device size.
3Measurement precision
If single transistor output is amplified to measure radiation changes, then measurement is possible, but the small output change requires complex detection circuitry
Solution Approach 1:
The patent segments the radiation signal into two parallel paths through the first and second transistors. By processing the signal through two separate transistor paths and then comparing their outputs, the system converts a small signal change into a differential signal that is easier to amplify and detect, reducing the complexity of the required detection circuitry.
Solution Approach 2:
The patent creates a copy of the radiation signal path through the second transistor with different conductivity type. This copied path allows the system to measure the difference between two parallel signals, transforming the measurement of a small change into the measurement of a differential signal that requires less complex detection circuitry.
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 dosimeter achieves enhanced sensitivity and a smaller form factor, allowing for more widespread and economical radiation detection with improved amplification of radiation measurements without exceeding supply voltage limits, outperforming conventional RADFETs in sensitivity and cost-effectiveness.
Implementation Method 1
A first transistor that is doped in accordance with a first conductivity type... A second transistor that is doped in accordance with a second conductivity type, different than the first conductivity type... The first and second transistors generate respective outputs that shift in opposite directions in response to radiation
Data Source
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AI summary
A dosimeter and an associated method for detecting radiation are provided. A dosimeter includes a complementary pair of transistors, such as a first transistor that is doped in accordance with a first conductivity type, such as an n-doped metal oxide semiconductor field effect transistor (MOSFET) and a second transistor that is doped in accordance with a second conductivity type, different than the first conductivity type, such as a p-doped MOSFET. The first and second transistors may be configured to generate respective outputs that shift in opposite directions in response to radiation. The dosimeter may also include a circuit element configured to determine a measure of the radiation based upon a difference between the respective outputs of the first and second transistors. The circuit element may include an amplifier configured to amplify the difference between the respective outputs of the first and second transistors.