Solid-State Imaging Device Current Source Circuit Topology
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Solution Overview
Problem
Conventional solid-state imaging devices struggle to achieve both high frame rates and low noise levels simultaneously, especially in capturing dark scenes, due to increased noise from signal amplification.
Innovation Solution
A solid-state imaging device with a current source comprising multiple transistors connected in series and a second transistor for short-circuiting at least one of the series-connected transistors, allowing increased current flow through the column signal line while canceling bias voltage variations, thereby enabling high-speed transmission with reduced noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If one transistor is connected to a column signal line to enhance current capability for high-speed transmission, then transmission speed is improved, but noise suppression capability deteriorates
Solution Approach 1:
The current source is divided into multiple parallel current source circuits, each consisting of series-connected transistors. This segmentation allows the system to achieve high current capability through parallel aggregation while each individual circuit maintains low noise characteristics through series connection, thus resolving the contradiction between speed and noise suppression.
2Object-generated harmful factors
If multiple transistors are connected in series in the current source, then noise is suppressed, but transmission speed deteriorates
Solution Approach 1:
Multiple current source circuits are connected in parallel to merge their current capabilities. Each circuit contains transistors connected in series for noise suppression, while the parallel combination of multiple such circuits achieves the required total current capability for high-speed transmission, thus resolving the contradiction between noise suppression and transmission speed.
3Productivity
If current capability is enhanced for high-speed transmission, then frame rate is improved, but power consumption increases
Solution Approach 1:
The current source circuits operate in a periodic manner, enhancing current capability only during the brief periods when pixel signal reading is required, rather than maintaining high current continuously. This periodic enhancement achieves high frame rates while minimizing overall power consumption by avoiding continuous high-power operation.
Data Source
AI summary
A solid-state imaging device according to an aspect of the present invention includes: an imaging area including a plurality of pixels arranged in rows and columns, each of the plurality of pixels converting incident light into a pixel signal; a column signal line provided for each of the columns, for reading out the pixel signal; and a current source connected to the column signal line, in which the current source includes: three transistors connected in series and provided between the column signal line and a GND line; and a transistor having a drain and a source each of which is connected to a different one of connection points connecting adjacent ones of the three transistors.