Solid-State Imaging Pixel Circuit with Potential Raising Transistors
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional solid-state imaging apparatuses face challenges in maintaining a high dynamic range when the power supply voltage is reduced, leading to difficulties in signal reading and increased power consumption due to potential fluctuations and transistor degradation.
Innovation Solution
The apparatus includes a pixel array with a photoelectric conversion element, transfer, reset, and amplifying transistors, along with control transistors that apply a higher potential to the signal line and pixel power supply during signal transfer, utilizing capacitance to increase the floating diffusion potential without degrading the amplifying transistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power supply voltage is reduced to decrease power consumption, then power consumption is reduced, but it becomes difficult to stably obtain a high dynamic range
Solution Approach 1:
The signal line potential raising transistor raises the potential of the signal line before signal charge transfer occurs. This preliminary action prepares the floating diffusion region to receive signal charges effectively even when the power supply voltage is reduced, thereby maintaining high dynamic range while operating at lower power consumption levels
Solution Approach 2:
The invention changes the potential parameter of the signal line by introducing a controllable transistor that adjusts the signal line potential to a higher level during specific operation phases. This parameter change enables the system to maintain adequate voltage headroom for high dynamic range operation while the overall power supply voltage is reduced
2Use of energy by moving object
If the power supply voltage is excessively reduced, then power consumption decreases, but signal reading becomes difficult
Solution Approach 1:
Before signal charge transfer, the signal line potential raising transistor pre-charges the signal line to a higher potential level. This preliminary action ensures that when signal charges are transferred to the floating diffusion region, there is sufficient potential difference to enable effective signal reading even with reduced power supply voltage
Solution Approach 2:
The signal line potential raising transistor acts as an intermediary that decouples the signal line potential from the main power supply voltage. It provides an elevated potential level specifically when needed for signal transfer, enabling signal reading to proceed effectively without requiring the entire system to operate at high voltage
3Device complexity
If conventional transistors are used in the pixel circuit, then device complexity is low, but potential fluctuations cause transistor degradation
Solution Approach 1:
The pixel circuit is segmented by separating the signal line potential control function into a dedicated transistor component. This segmentation allows the potential raising transistor to independently manage signal line potential without interfering with the normal operation of other pixel transistors, thereby reducing potential fluctuations and degradation while adding minimal overall complexity
Solution Approach 2:
The signal line potential raising transistor serves as a protective intermediary that isolates the main pixel circuit transistors from harmful potential fluctuations. By controlling the signal line potential separately, it prevents voltage stress and degradation in the amplifying and transfer transistors, enhancing their reliability without significantly increasing circuit complexity
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 configuration allows for a reduction in power supply voltage while maintaining a high dynamic range and ensuring transistor reliability by minimizing potential differences across the amplifying transistor.
Implementation Method 1
each of the plurality of the pixel cells including a photoelectric conversion element
Implementation Method 2
the potential FD of the FD portion 4 capacitively coupled with the signal output line 12 by a potential fluctuation of this signal output line 12 is increased by ΔV1
Data Source
AI summary
A solid-state imaging apparatus includes a plurality of pixel cells arranged in a pixel array unit, a vertical signal line and a pixel power supply line each connected to a source electrode and a drain electrode of an amplifying transistor, a Pch transistor for supplying potential AVDD to the vertical signal line, a Pch transistor for supplying potential PBIAS_H higher than the potential AVDD to the vertical signal line, a Pch transistor for supplying the potential PBIAS_H to the pixel power supply line, wherein while the transfer transistor is turned ON and transfers signal charges photoelectrically converted by a photodiode to the floating diffusion portion, the Pch transistors are turned ON and the potential PBIAS_H is applied to the vertical signal line and the pixel power supply line.