Electrostatic Protection Circuit Node Potential Control
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Solution Overview
Problem
Conventional electrostatic protective circuits can experience dielectric breakdown even when the signal potential is below the breakdown voltage due to rapid changes, caused by parasitic capacitance that prevents the potential at a node from following the signal potential, leading to excessive inverse bias and potential deformation.
Innovation Solution
Incorporating a field effect transistor (FET) coupled between the protective elements, with its source and bulk connected between the protective elements and the power supply, and its gate connected to the signal line, allowing the potential at the node to follow rapid changes in signal potential and preventing dielectric breakdown.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bipolar transistors are used as protective elements in series between signal line and power supply, then electrostatic protection is provided, but dielectric breakdown occurs when signal potential changes rapidly due to parasitic capacitance
Solution Approach 1:
An FET is introduced as an intermediary element coupled to the node between the bipolar transistors. The FET acts as a mediator that actively controls the potential at this node, preventing the parasitic capacitance from causing excessive voltage spikes. The FET's gate is connected to the signal line, allowing it to respond to rapid potential changes and maintain the node potential within safe limits, thus preventing dielectric breakdown while preserving the electrostatic protection function.
2Ease of operation
If parasitic capacitance is present at the node between protective elements, then circuit operation is enabled, but potential deformation occurs during rapid signal changes
Solution Approach 1:
The FET implements a feedback mechanism by connecting its gate to the signal line and its source/bulk to the node between the bipolar transistors. This configuration allows the FET to continuously monitor the signal potential and adjust the node potential in real-time. When rapid potential changes occur, the FET responds by conducting current to maintain the node potential, providing negative feedback that stabilizes the composition and prevents potential deformation.
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 effectively prevents dielectric breakdown of the protective elements by ensuring the potential at the node aligns with signal potential changes, even if the signal potential is below the breakdown voltage, thereby maintaining a stable waveform and reducing the risk of snapback phenomena.
Implementation Method 1
a channel formation region 114 which forms a channel between the source and the drain; wherein an n-type impurity is added in the channel formation region 114 in an activated state
Implementation Method 2
a parasitic capacitance C1 is created between the node N and the ground
Data Source
AI summary
An electrostatic protective circuit includes a bipolar transistor, a bipolar transistor and an FET. The bipolar transistors and are coupled in series between a signal line and the ground (GND). The FET is configured that a source and a bulk thereof are coupled to a node N situated between the bipolar transistors, a gate is coupled to the signal line, and a drain is coupled to the power supply.