NPN Bipolar Transistor TVS with Optimized Junctions
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Solution Overview
Problem
Existing high surge transient voltage suppressors (TVS) face challenges in achieving low leakage current while maintaining robust clamping voltage and tunable breakdown voltage, especially for protecting power supply pins and data pins in electronic devices, as increased base doping to reduce leakage current compromises bipolar transistor gain and clamping voltage.
Innovation Solution
The implementation of bidirectional and unidirectional TVS devices using NPN bipolar transistors with optimized collector-base and emitter-base junctions, which are spatially distributed and individually optimized, allowing for avalanche mode breakdown and resistive coupling to a PN junction diode in reverse bias, enabling low leakage current and robust clamping voltage with tunable breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If base doping level is increased to reduce leakage current, then leakage current decreases, but bipolar transistor gain decreases and clamping voltage is compromised
Solution Approach 1:
The patent applies local quality by differentiating the doping levels in specific regions of the bipolar transistor. The base region has higher doping to reduce leakage current, while the emitter and collector regions maintain lower doping to preserve gain and clamping voltage. This spatial variation in doping quality allows simultaneous optimization of leakage current and clamping voltage performance.
Solution Approach 2:
The patent utilizes parameter changes by adjusting the doping concentration levels in different regions of the transistor. Specifically, the base doping level is increased to reduce leakage current, while the emitter and collector doping levels are optimized to maintain sufficient gain and clamping voltage. This selective parameter modification resolves the contradiction between leakage current reduction and clamping voltage maintenance.
2Object-generated harmful factors
If base doping is increased to achieve low leakage current, then leakage current is reduced, but bipolar injection efficiency decreases
Solution Approach 1:
The patent implements local quality by applying different doping strategies to different regions. The base region receives higher doping to minimize leakage current, while the emitter region maintains lower doping to ensure high injection efficiency. This localized differentiation allows the device to achieve low leakage without sacrificing bipolar injection efficiency.
Solution Approach 2:
The patent employs parameter changes by selectively modifying the doping concentration in the base region while maintaining appropriate doping levels in the emitter and collector. This controlled parameter adjustment reduces leakage current through the base while preserving the injection efficiency required for effective transient voltage suppression.
3Reliability
If TVS provides high surge protection, then protection capability is improved, but capacitance increases which may interfere with data speed
Solution Approach 1:
The patent applies parameter changes by optimizing the physical dimensions and doping concentrations of the bipolar transistor to achieve a favorable capacitance value. The device structure and material parameters are carefully selected to provide high surge protection capability while maintaining low capacitance that does not interfere with high-speed data transmission.
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
The solution provides effective high surge protection with low leakage current and robust clamping voltage, ensuring the protection of electronic devices from transient voltage events while allowing for optimized breakdown voltage settings based on the device's operating conditions.
Implementation Method 1
allowing for avalanche mode breakdown
Data Source
AI summary
A bidirectional transient voltage suppressor is constructed as an NPN bipolar transistor incorporating optimized collector-base junction realizing avalanche mode breakdown. In some embodiments, the bidirectional transient voltage suppressor is constructed as an NPN bipolar transistor incorporating individually optimized collector-base and emitter-base junctions with the optimized junctions being spatially distributed. The optimized collector-base and emitter-base junctions both realize avalanche mode breakdown to improve the breakdown voltage of the transistor. Alternately, a unidirectional transient voltage suppressor is constructed as an NPN bipolar transistor with a PN junction diode connected in parallel in the reverse bias direction to the protected node and incorporating individually optimized collector-base junction of the bipolar transistor and p-n junction of the diode.