Dual-Control MOSFET Resistor for Wide-Range Stable Resistance
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Solution Overview
Problem
Existing electronically-controlled resistors (ECRs) face limitations in achieving accurate resistance control due to a narrow voltage range, temperature dependence, and instability under destabilizing factors, particularly failing to maintain stable resistance across a wide temperature range and unable to handle small resistance values effectively.
Innovation Solution
The proposed ECR design incorporates a voltage converter with three inputs, an instrument resistor, and an executive element, featuring logarithmators, an adder, an additional subtractor, and an exponential converter, allowing for precise control of resistance through direct or inverse dependence on controlling voltage, and enabling both analog and digital control signals, with an executive element capable of passing large currents to achieve small resistance values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a MOSFET is used as an electronically-controlled resistor, then resistance control is achieved, but the voltage range for linear dependence is narrow
Solution Approach 1:
The control voltage is segmented into two independent inputs: a first controlling voltage for setting the desired resistance value and a second controlling voltage for compensating temperature effects. This segmentation allows each voltage to perform a specific function, expanding the operational voltage range while maintaining linear dependence.
Solution Approach 2:
A temperature compensation circuit is introduced as an intermediary between the MOSFET and the control voltage source. This circuit receives the second controlling voltage and generates a compensation signal that adjusts the gate voltage to counteract temperature-induced resistance changes, thereby extending the effective voltage range.
2Ease of operation
If a MOSFET is used to control resistance, then resistance adjustment is possible, but temperature dependence causes instability
Solution Approach 1:
A temperature compensation feedback loop is implemented where the second controlling voltage is adjusted based on detected temperature changes. The compensation circuit continuously monitors temperature effects and feeds back adjustment signals to the MOSFET gate, maintaining stable resistance despite temperature variations.
Solution Approach 2:
The control system dynamically changes the gate voltage parameter in response to temperature changes. By varying the second controlling voltage based on temperature, the system compensates for the MOSFET's inherent temperature dependence, transforming a fixed-parameter device into a dynamically adjustable one that maintains stability.
3Ease of operation
If conventional ECR designs are used, then resistance control is achieved, but accuracy is insufficient under destabilizing factors
Solution Approach 1:
A compensation circuit acts as an intermediary that receives a second controlling voltage and generates correction signals. This intermediary process separates the primary resistance control function from the temperature compensation function, allowing each to be optimized independently and improving overall accuracy.
Solution Approach 2:
The system dynamically adjusts multiple parameters: the first controlling voltage sets the nominal resistance value while the second controlling voltage dynamically adjusts the gate voltage to compensate for temperature drift. This dual-parameter control approach significantly improves resistance accuracy under varying conditions.
4Ease of operation
If MOSFET resistance is controlled, then circuit resistance changes, but dependence on source-drain voltage limits applicability
Solution Approach 1:
The temperature compensation circuit implements feedback that adjusts the gate voltage based on temperature and controlling voltages, not on the source-drain voltage. This feedback mechanism decouples the resistance control from the source-drain voltage dependence, allowing the resistor to maintain its set value across different operating voltages.
Solution Approach 2:
The control function is segmented into two independent voltage inputs that collectively compensate for all sources of resistance variation, including source-drain voltage effects. This segmentation allows the system to maintain voltage independence by adjusting the gate voltage through the controlling voltages rather than being passively dependent on source-drain voltage changes.
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
This design widens the range of resistance values, particularly allowing for low resistance settings while maintaining stability across varying temperatures, enabling precise resistance control and tolerance to destabilizing factors, including temperature changes, and supporting both direct and inverse voltage dependencies.
Implementation Method 1
a voltage converter with three inputs, an instrument resistor, and an executive element
Implementation Method 2
As the controlling voltage varies, so does the resistance of the FET channel
Data Source
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AI summary
An electronically-controlled resistor (ECR) for controlled changing of resistance of a portion of an electric circuit is provided with a terminal for connecting to a first source of controlling voltage and comprises a voltage converter, an instrument resistor, and a subtractor. Additionally, the ECR is provided with another terminal for connecting to a second source of controlling voltage and comprises an executive element having three terminals and connecting consistently with an instrument resistor. A first one is connected to a first terminal of the instrument resistor, a second terminal is connected to an output of the subtractor, and a third terminal is connected to a high-potential terminal of the ECR. The voltage converter represents electronical component adapted to convert incoming signals from the controlling voltage sources and the ECR high-potential terminal into an intermediate signal applied from an output of the voltage converter. The value of the intermediate signal is equivalent to a product of the voltage at the ECR high-potential terminal by quotient of the controlling voltages by each other. The ECR makes it possible to achieve a wide range of values of the preferred values of ECR resistance, down to ultra-small values thereof while maintaining tolerance to destabilizing factors, including temperature.