Radiation Detector Reset Circuit for Current Stabilization
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Solution Overview
Problem
Active pixel type radiation detectors face challenges in maintaining a desired Signal/Noise ratio due to variations in threshold voltage and mobility of amplifying transistors, leading to issues with initial current values and output signal detection.
Innovation Solution
A radiation detector design that includes a sensor element generating electrical signals from incident radiation, an amplifying transistor, and a reset reading circuit with an amplifier to read and adjust the current value between the source and drain electrodes of the amplifying transistor, ensuring the current value remains within a predetermined range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If an initial value of gate voltage is uniformly determined, then the device complexity is reduced, but the measurement precision of current value varies due to transistor parameter variations
Solution Approach 1:
The patent applies preliminary action by measuring and storing the initial current value (before radiation exposure) for each pixel. This pre-measured baseline is then used to calculate the radiation-induced current change, eliminating the need for complex real-time threshold voltage compensation while maintaining measurement precision.
Solution Approach 2:
The patent changes the approach from controlling gate voltage parameters to measuring and utilizing current value parameters. By focusing on current measurements at different states (before and after radiation), the system achieves accurate radiation detection without needing to precisely control or know the exact gate voltage threshold of each transistor.
2Reliability
If the initial current value is increased to improve signal amplification, then the Signal/Noise ratio improves, but the output signal saturates and loses detection capability
Solution Approach 1:
The patent uses partial action by measuring only the change in current value rather than relying on the absolute current level. By calculating the difference between initial and final current measurements, the system can use sufficient amplification to ensure detectable signals while avoiding saturation, since only the incremental change matters.
Solution Approach 2:
The system implements feedback by using the measured initial current value to establish a baseline for comparison. This feedback mechanism allows the system to determine radiation-induced changes accurately regardless of the absolute current level or amplification settings, preventing saturation issues.
3Measurement precision
If the initial current value is decreased to avoid saturation, then the output signal remains detectable, but the amplification factor becomes too small resulting in poor Signal/Noise ratio
Solution Approach 1:
The patent applies partial action by measuring only the change in current value rather than relying on the absolute current level. By calculating the difference between initial and final current measurements, the system can use sufficient amplification to ensure detectable signals while avoiding saturation, since only the incremental change matters.
4Measurement precision
If a reset reading circuit with amplifier is added to read current values, then the measurement precision improves, but the device complexity increases
Solution Approach 1:
The patent applies universality by designing the reset reading circuit to perform multiple functions: it measures the initial current value, stores it as a baseline, and then measures the current value after radiation exposure. This multi-functional approach consolidates what could be separate circuits into a single integrated unit, reducing overall complexity while maintaining measurement precision.
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
This approach allows for consistent output signals with a desired Signal/Noise ratio even with varying threshold voltage and mobility, preventing saturation and ensuring accurate detection.
Implementation Method 1
a direct conversion type that directly converts X-rays into an electrical signal
Implementation Method 2
an indirect conversion type that converts X-rays into light by using a scintillator
Implementation Method 3
the light is converted into an electrical signal by using a photoelectric conversion element
Data Source
AI summary
A radiation detector (radiation sensor 1) includes a sensor element (3) and an amplifying transistor (5), reads a current value that flows between the drain and the source based on a change in voltage of a gate electrode of the amplifying transistor (5), and also includes a reset reading circuit (10) that includes an amplifier (11) and reads the current value, and the reset reading circuit (10) outputs an initial voltage to the gate electrode so that the current value becomes a value that is determined in advance.