Diode-Connected BJT Bandgap Reference Voltage Circuit
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Solution Overview
Problem
Existing reference voltage circuits using bipolar junction transistors in integrated circuits face challenges in maintaining a constant reference voltage across varying power supply voltages and temperature conditions, which can lead to malfunctions and reduced integration density.
Innovation Solution
The design incorporates diode-connected bipolar junction transistors with a common collector and base region, and multiple emitter regions arranged in island shapes, coupled in parallel to generate a band gap reference voltage that is insensitive to temperature variations by balancing positive and negative temperature coefficients through appropriate resistor adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If bipolar junction transistors are employed in the BGR circuit to generate stable reference voltage, then temperature stability is improved, but integration density is degraded
Solution Approach 1:
The patent merges multiple bipolar junction transistors into a single integrated structure where multiple emitter regions share common base and collector regions. This consolidation achieves the temperature compensation function of multiple transistors while reducing the overall area occupation, thereby improving integration density without sacrificing temperature stability.
Solution Approach 2:
The patent implements a nested structure where multiple emitter regions are arranged within a shared common base region and common collector region. This nested configuration allows multiple functional elements to occupy overlapping spatial domains, reducing the total area required while maintaining the temperature compensation characteristics of the BGR circuit.
2Reliability
If power supply voltage varies, then circuit operation becomes unstable, but increasing voltage regulation complexity increases device complexity
Solution Approach 1:
The diode-connected bipolar junction transistor structure provides automatic voltage regulation through its inherent diode characteristics. The base-emitter junction acts as a natural voltage reference that self-adjusts to maintain stable operation, eliminating the need for complex external voltage regulation circuits.
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 ensures a stable and constant reference voltage across temperature variations, enhancing the integration density and reliability of the circuits while maintaining robustness against power supply voltage fluctuations.
Implementation Method 1
a voltage difference between the emitter-base voltages of the pair of bipolar junction transistors may have a negative temperature coefficient. If the positive temperature coefficient and the negative temperature coefficient may be appropriately controlled to have the same absolute value, the reference voltage circuit may generate a constant reference voltage regardless of temperature variation
Data Source
AI summary
A diode-connected bipolar junction transistor includes a common collector region of a first conductivity, a common base region of a second conductivity disposed over the common collector region, and a plurality of emitter regions of the first conductivity disposed over the common base region, arranged to be spaced apart from each other, and arranged to have island shapes. The common base region and the common collector region are electrically coupled to each other.