Single-Line Sensor Output Circuit for Low Radio Wave Radiation
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Solution Overview
Problem
Existing sensor output circuits face challenges in reducing radio wave radiation when using single-line signal transmission due to lack of precise control over output current, especially in cost-restricted environments where differential signals are not feasible.
Innovation Solution
The solution involves connecting two MOS transistors in series at the output terminal, with one driven by a constant current and the other maintaining the drain terminal at a constant voltage, reducing radio wave radiation by minimizing current increase with voltage and enhancing breakdown voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If differential signal is used for output transmission, then noise radiation is reduced, but device complexity and cost increase
Solution Approach 1:
The patent changes the electrical parameters of the output circuit by introducing a constant current source to control the output current, and a voltage maintenance transistor to stabilize the drain voltage. These parameter changes allow single-line signal transmission to achieve noise radiation reduction normally requiring differential signals, without increasing device complexity
2Speed
If output current is increased for faster signal transmission, then transmission speed improves, but radio wave radiation increases
Solution Approach 1:
The patent implements feedback control through the voltage maintenance transistor (seventh MOS transistor) that monitors and stabilizes the drain voltage of the constant current transistor. This feedback mechanism ensures the output current remains precisely controlled at the required level, enabling fast signal transmission while preventing excessive radio wave radiation that would occur with uncontrolled current increases
3Object-generated harmful factors
If precise current control is implemented to reduce radio wave radiation, then harmful radiation is reduced, but device complexity increases
Solution Approach 1:
The patent introduces an intermediary voltage maintenance transistor (seventh MOS transistor) that acts as a mediator between the constant current source and the output. This intermediary component stabilizes the drain voltage of the constant current transistor, ensuring precise current control for radio wave radiation reduction while keeping the overall circuit structure simple and cost-effective
Data Source
AI summary
A sensor output circuit is limited with high accuracy, and reduces radio wave radiation by signal transmission using a single-line signal. The sensor output includes a pulse signal Vin that changes according to a physical quantity to be measured, MOS transistors that perform on/off operations according to the pulse signal Vin, a constant current source that generates a constant current, a MOS transistor which generates a gate voltage of a MOS transistor, MOS transistors which form a current mirror circuit, and the MOS transistor which works to maintain a drain voltage of the MOS transistor at a constant voltage, and the output terminal which is driven by the MOS transistors connected in series. In addition, an output signal from the sensor output circuit is transmitted to a control circuit via an output signal line. The control circuit includes a pull-up resistor, a capacitor, and an input gate circuit.