Bandgap Reference Circuit Using NMOS Breakdown for High Voltage Stability
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Solution Overview
Problem
High voltage analog circuits lack a temperature-independent and power-supply-independent bandgap reference voltage, which is essential for stable performance.
Innovation Solution
A bandgap reference circuit utilizing a combination of NMOS and bipolar junction transistors, along with a differential amplifier and voltage dividing unit, is designed to generate a reference voltage with minimal temperature and power supply dependence, employing a BCD process to achieve high voltage and low quiescent current operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a conventional bandgap reference circuit is used, then temperature independence is achieved, but high voltage operation capability is insufficient
Solution Approach 1:
The patent combines bipolar transistors (Q1, Q2, Q3) with NMOS transistors (M1, M2) and resistors to create a composite reference circuit structure. This composite approach allows the circuit to achieve both temperature independence through the bipolar transistor bandgap mechanism and high voltage operation capability through the NMOS transistor breakdown voltage characteristics, resolving the contradiction between temperature stability and high voltage capability
2Reliability
If high voltage transistors are used, then high voltage operation is achieved, but quiescent current increases
Solution Approach 1:
The patent utilizes the breakdown voltage parameter of NMOS transistor M1 as the reference voltage source. By operating M1 in breakdown mode and controlling its drain-source voltage through the feedback network (resistors R1-R4 and transistors Q1-Q3), the circuit achieves high voltage operation capability while maintaining low quiescent current consumption, as the breakdown current can be precisely controlled and is typically lower than the current required by conventional high voltage transistor configurations
3Stability of the object's composition
If a feedback loop is implemented, then temperature stability is improved, but circuit complexity increases
Solution Approach 1:
The feedback network in the patent serves multiple functions simultaneously: it controls the drain-source voltage of NMOS transistor M1 to maintain breakdown operation, it compensates for temperature variations through the bipolar transistor bandgap mechanism, and it regulates the reference voltage output. This multi-functionality approach achieves temperature stability without proportionally increasing circuit complexity, as the same feedback loop accomplishes multiple objectives
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 a stable bandgap reference voltage with low quiescent current and minimal variation across a wide power supply range, suitable for high voltage analog circuits, ensuring reliable performance despite temperature and power variations.
Implementation Method 1
The first voltage is related to a multiple of the base to emitter voltage differential (ΔVBE) of a pair of transistors Q1 and Q2 operating at different current densities, and the second voltage is related to the base to emitter voltage VBE of a transistor Q3
Implementation Method 2
the second voltage is related to the base to emitter voltage VBE of a transistor Q3. In FIG. 1, the transistors Q1, Q2 and Q3 are NPN type bipolar junction transistors. Furthermore, the first voltage ΔVBE is proportional to the absolute temperature (PTAT) and thus has a positive temperature coefficient, and the second voltage VBE has a negative temperature coefficient
Data Source
AI summary
A bandgap reference circuit is provided. An input node receives a supply voltage. An output node provides a reference voltage. A first transistor is coupled between the input node and the output node and has a first control terminal. A resistor is coupled between the input node and the first control terminal. A second transistor is coupled to the first control terminal and has a second control terminal coupled to the output node. A third transistor is coupled between the second transistor and a ground terminal and has a third control terminal. A voltage dividing unit provides a first voltage and a second voltage according to the reference voltage. A differential amplifier provides a signal to the third control terminal according to a difference between the first and second voltages.