Depletion-Type Selecting Transistor Noise Reduction in Imaging Pixels
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Solution Overview
Problem
Solid-state imaging devices and other physical quantity detecting devices face challenges with noise (1/f noise and burst noise) due to the finite on-resistance of selecting transistors, which are not effectively addressed by existing solutions, and these solutions also increase manufacturing costs and module size.
Innovation Solution
The use of depletion-type transistors as selecting transistors in pixels, which reduces on-resistance and noise by allowing current to flow through the bulk side rather than the oxide film interface, and applying a negative voltage when the transistor is turned off to interrupt current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gate voltage of the selecting transistor is raised to reduce on-resistance, then the on-resistance decreases, but noise (1/f noise and burst noise) increases significantly
Solution Approach 1:
The patent changes the type parameter of the selecting transistor from enhancement-type to depletion-type. This parameter change fundamentally alters the transistor's electrical characteristics, enabling it to achieve low on-resistance without requiring high gate voltages, thereby avoiding the generation of excessive noise at the oxide film interface.
2Reliability
If a boosting circuit is added to raise the power supply voltage for the selecting transistor, then the on-resistance is reduced, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts and eliminates the need for the boosting circuit by changing the transistor type. The depletion-type selecting transistor inherently provides the required low on-resistance without external voltage boosting, thereby removing the complex boosting circuit and its associated manufacturing costs.
3Reliability
If the gate voltage is raised to overcome the threshold value reduction, then the on-resistance is reduced, but the power consumption increases
Solution Approach 1:
The patent changes the transistor type parameter to depletion-type, which has different voltage-current characteristics. This allows the transistor to maintain low on-resistance at lower gate voltages, thereby reducing the power consumption compared to enhancement-type transistors that require higher voltages.
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 reduces 1/f noise and burst noise while maintaining low power supply voltage and preventing increases in manufacturing costs, module size, and power consumption, effectively addressing the noise issues without raising the gate voltage.
Implementation Method 1
The use of depletion-type transistors as selecting transistors in pixels, which reduces on-resistance and noise by allowing current to flow through the bulk side rather than the oxide film interface
Data Source
AI summary
A physical quality detecting device including: a detecting unit that detects a physical quantity supplied from the outside with photo-converting pixels which are two-dimensionally arranged, each of which has a selecting transistor for outputting a signal from the detecting unit to a signal line. In the physical quality detecting device, the selecting transistor is a depletion-type transistor. The signal line is selectively coupled to a reference voltage.