FDSOI Voltage Divider Using Back-Gate Bias for Low-Power Stability
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Solution Overview
Problem
Ring oscillators face challenges in controlling and stabilizing oscillating frequency due to variations in supply voltage and temperature, leading to bulky and costly reference resistors, which are also sensitive to temperature changes, affecting low-power applications and silicon surface usage.
Innovation Solution
An electronic voltage divider circuit using FDSOI transistors with back-gate biases to form a current mirror structure, reducing the voltage across a load resistor while maintaining low current values, thus minimizing silicon surface bulk and temperature sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a high-value reference resistor is used to reduce current consumption in low-power oscillators, then power consumption decreases, but the silicon surface area occupied by the resistor increases significantly
Solution Approach 1:
The invention changes the operating parameters of FDSOI transistors by applying specific back-gate voltages to modify their threshold voltages and transfer characteristics. This allows the transistors to operate in weak inversion mode, enabling the circuit to achieve low current consumption without requiring large high-value resistors, thus reducing the silicon surface area while maintaining low power consumption
Solution Approach 2:
The invention replaces the traditional mechanical/resistive voltage division approach with an electronic approach using FDSOI transistors operating in weak inversion. The transistors' inherent exponential current-voltage characteristics in weak inversion mode provide the voltage division function, eliminating the need for bulky physical resistors and reducing the silicon footprint
2Ease of operation
If a reference resistor is used in oscillator circuits, then frequency control is enabled, but the oscillator becomes sensitive to temperature variations
Solution Approach 1:
The invention uses the back-gate voltage control mechanism to create a feedback system that compensates for temperature variations. By monitoring and adjusting the back-gate voltages applied to the FDSOI transistors, the circuit maintains stable transfer characteristics and threshold voltages across temperature changes, thereby stabilizing the oscillator frequency while preserving frequency control capability
Solution Approach 2:
The invention dynamically adjusts the back-gate voltages of the FDSOI transistors to compensate for temperature-induced parameter changes. This parameter adjustment mechanism maintains consistent transistor characteristics across temperature variations, enabling temperature-insensitive frequency control in oscillator circuits
3Object-affected harmful factors
If FDSOI transistors with back-gate control are used to create a voltage divider, then temperature insensitivity is achieved, but the device complexity increases
Solution Approach 1:
The invention makes the FDSOI transistor back-gate control mechanism serve multiple functions: it provides temperature compensation, enables precise voltage division, and allows for threshold voltage adjustment. This multi-functionality reduces the need for separate compensation circuits and additional components, thereby achieving temperature insensitivity without proportionally increasing device complexity
Solution Approach 2:
The FDSOI transistors' back-gate control capability is used to automatically compensate for temperature effects and maintain stable operation. The transistors self-regulate their characteristics through the back-gate voltage mechanism, eliminating the need for external temperature compensation circuits and reducing overall system complexity while achieving temperature insensitivity
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 achieves a stable voltage divider with reduced silicon surface usage and temperature insensitivity, enabling efficient low-power operation and frequency control in ring oscillators and other applications.
Implementation Method 1
the back-face gate of the first transistor of the second type is brought to a potential lower than that of the back-face gate of the second transistor of the second type if these two transistors are of nMOS type, and that the back-face gate of the first transistor of the second type is brought to a potential greater than that of the back-face gate of the second transistor of the second type if these two transistors are of pMOS type
Data Source
AI summary
A voltage divider circuit includes at least two FDSOI transistors (TP1, TP2) of a first type connected to a first supply potential and arranged in a current mirror structure, two FDSOI transistors (TN1, TN2) of a second type and an electrical load (R), the drain of a first—respectively second—transistor (TN1) of the second type being connected to the drain of a first—respectively second—transistor (TP1) of the first type, the drain of the first transistor of the second type being connected to the front-face gate of this same transistor, the front-face gates of the first and second transistors of the second type being connected to one another, the source of the first transistor of the second type being connected to a second supply potential and the load being placed between the source of the second transistor of the second type and the second supply potential. The back-face gates of the first and second transistors of the second type (TN2) are connected to an external circuit applying an input voltage between these two back-face gates, the voltage across the terminals of the load (VRO) constituting an output voltage equal to a fraction of the input voltage.