Shift Register Circuit Double-Gate Transistor Threshold Voltage Stability
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Solution Overview
Problem
Existing active matrix display devices face characteristic degradation due to fluctuations in threshold voltage of thin film transistors (TFTs), which current compensation methods struggle to address effectively, often requiring high voltages and additional threshold adjusting circuits.
Innovation Solution
A shift register circuit with double-gate transistors is implemented, where the second gate electrode is controlled to apply inverse logic states or specific voltages based on the first gate electrode's state, reducing characteristic degradation by suppressing threshold voltage fluctuations and promoting recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a double-gate structure TFT with back gates is used to compensate for threshold voltage fluctuations, then the threshold voltage fluctuation is compensated, but high voltages of several dozen volts must be applied to the back gates and a threshold adjusting circuit is required
Solution Approach 1:
The invention extracts and addresses only the critical threshold voltage fluctuation problem during specific operation periods (when voltage is applied to gate electrodes) rather than attempting continuous compensation. This selective approach eliminates the need for complex threshold adjusting circuits while maintaining reliability by focusing compensation efforts where they are most needed.
Solution Approach 2:
The invention changes the operational parameters of the double-gate TFT by applying control voltages to back gates only during specific time periods when voltage is applied to the gate electrodes. This dynamic parameter adjustment reduces the required voltage magnitude compared to continuous compensation methods, eliminating the need for high voltage application while maintaining threshold voltage stability.
2Reliability
If continuous threshold voltage compensation is applied, then threshold voltage stability is improved, but power consumption increases due to constant high voltage application
Solution Approach 1:
The invention applies control voltages to the back gates periodically - specifically during time periods when voltage is applied to the gate electrodes - rather than continuously. This periodic action maintains threshold voltage stability during critical operation periods while significantly reducing power consumption by eliminating voltage application during non-critical periods.
Solution Approach 2:
The invention applies control voltages to the back gates in advance during time periods when voltage is applied to the gate electrodes, preventing threshold voltage fluctuations before they occur rather than correcting them after. This preliminary action ensures threshold stability during critical periods while minimizing the duration of voltage application to reduce power consumption.
Data Source
AI summary
A shift register circuit has a plurality of unit circuits that are cascade-connected to one another and that output received pulse signals as output signals in accordance with a clock signal, the shift register circuit sequentially outputting the output signals from the plurality of respective unit circuits. The output circuits each include a double-gate transistor having first gate electrode that controls conductivity between the drain electrode and the source electrode, and a second gate electrode formed through an insulating layer and disposed to face the first gate electrode across a semiconductor layer between the drain electrode and the source electrode. The shift register circuit applies a prescribed voltage to the second gate electrode in accordance with a voltage applied to the first gate electrode.