MOSFET Level Converter With Fixed Source-Drain Voltage Linearity
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Solution Overview
Problem
Conventional analog level converters with high input impedance suffer from non-linear operation due to variable source-drain voltage, limiting their use in highly linear circuits, while those with low input impedance or near power supply measurement limitations restrict their application.
Innovation Solution
A level converter design that stabilizes the source-drain voltage of a transistor using a reference voltage, combined with a constant drain current and threshold voltage, achieving high linearity and input impedance, and allowing measurement against a power supply, utilizing an impedance converter, such as a differential amplifier, to maintain a predefined source-drain voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional MOSFET-based level converter with high input impedance is used, then the input impedance is high, but the linearity deteriorates due to variable source-drain voltage
Solution Approach 1:
The patent employs a feedback mechanism where the source-drain voltage is continuously monitored and adjusted through the bulk terminal connection to maintain a constant voltage level. This feedback loop compensates for variations in source-drain voltage, thereby improving linearity while preserving the high input impedance characteristic of MOSFET-based level converters.
Solution Approach 2:
The patent changes the operating parameters by maintaining a constant source-drain voltage through the bulk terminal connection. This parameter stabilization transforms the transistor's operation point, enabling highly linear level conversion. The constant voltage parameter, combined with constant drain current, ensures that the source-gate voltage remains stable, directly improving linearity.
2Measurement precision
If a conventional level converter design is used, then high input impedance is achieved, but the ability to be measured against power supplies is limited
Solution Approach 1:
The patent introduces an impedance converter as an intermediary component that enables accurate measurement against power supplies. This intermediary device bridges the gap between the high-impedance level converter and the measurement system, allowing precise measurements to be taken without compromising the converter's high input impedance or limiting its application versatility.
3Stability of the object's composition
If the source-drain voltage is allowed to vary, then the circuit simplicity is maintained, but the source-gate voltage stability deteriorates
Solution Approach 1:
The feedback connection to the bulk terminal provides automatic stabilization of the source-gate voltage without requiring complex external control circuits. The feedback mechanism inherently compensates for voltage variations, achieving stability while adding minimal circuit complexity.
Solution Approach 2:
The transistor's bulk terminal is utilized as a self-service element to automatically regulate and stabilize the source-gate voltage. This self-regulating mechanism eliminates the need for additional complex stabilization circuits, maintaining circuit simplicity while achieving the desired voltage stability.
Data Source
AI summary
A level converter and circuit arrangement comprising such level converters. The level converter comprises a transistor, an impedance converter, an input voltage connection, an output voltage connection, and a power supply connection. The input voltage connection is connected to a gate terminal of the transistor. The output voltage connection is connected to a source terminal of the transistor and to the power supply connection. A first input terminal of the impedance converter is connected to the source connection or to the gate terminal of the transistor. An output terminal of the impedance converter is connected to the drain terminal of the transistor. The power supply connection is equipped to receive a current from a constant current source. The impedance converter is equipped to keep a source-drain voltage of the transistor at a predefined value using a reference voltage.