Bandgap Reference Voltage Using PTAT and CTAT Transistor Stacks
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Solution Overview
Problem
Existing reference voltages vary with temperature, leading to errors and instability in devices, particularly in applications like analog-to-digital converters and voltage regulators.
Innovation Solution
A semiconductor device generates a temperature-independent reference voltage using a combination of proportional to absolute temperature (PTAT) and complementary to absolute temperature (CTAT) circuits, utilizing field-effect transistors with matched voltage thresholds, to create a stable reference voltage through a bandgap circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional reference voltage is used, then the device can operate with simple circuitry, but the reference voltage varies with temperature causing errors and instability
Solution Approach 1:
The reference voltage generation is divided into two independent temperature-dependent voltage generators (PTAT and CTAT circuits), each generating a voltage with a specific temperature coefficient. By segmenting the function into separate modules with complementary temperature characteristics, the patent achieves temperature compensation while maintaining modular circuit architecture.
Solution Approach 2:
The patent combines two different voltage generation circuits (PTAT and CTAT) with opposite temperature coefficients to create a composite reference voltage system. The PTAT circuit generates a voltage that increases with temperature, while the CTAT circuit generates a voltage that decreases with temperature, and their combination produces a temperature-independent reference voltage through weighted summation.
2Measurement precision
If a temperature-independent reference voltage is generated using PTAT and CTAT circuits, then reference voltage stability across temperature is achieved, but the device complexity increases
Solution Approach 1:
The patent adjusts the temperature coefficients of the PTAT and CTAT circuits by modifying circuit parameters such as transistor dimensions, resistor values, and current ratios. By changing these parameters, the patent optimizes the temperature compensation characteristics to achieve high accuracy (3-sigma accuracy of less than 5%) while controlling the complexity of individual circuit blocks.
Data Source
AI summary
A voltage generator includes a temperature-dependent voltage generator and a reference voltage node. The temperature-dependent voltage generator generates a voltage that increases with temperature and includes a first transistor stack and a second transistor stack, each of which has a first source/drain terminal and a gate terminal connected to each other at a temperature-dependent voltage generator node. The reference voltage node is connected to the temperature-dependent voltage generator and provides a reference voltage substantially independent of temperature. A method for generating the temperature-independent reference voltage is also disclosed.