Reference Resistor Impedance Conversion With Fractional Current
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Solution Overview
Problem
Current technologies fail to produce high-value resistors with impedance values greater than 1 MΩ that operate in continuous time, maintaining low stray capacitance, high noise density, and large voltage swing while being thermally stable and area-efficient.
Innovation Solution
An electronic device modifies the impedance value of a reference resistor by applying a fraction of the current flowing through it between two terminals, using current mirrors with differently dimensioned FET transistors to achieve high impedance values, low stray capacitance, and voltage independence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If integrated physical resistors are used to achieve high impedance values, then the impedance value increases, but the stray capacitance increases and the resistor size becomes too large
Solution Approach 1:
The patent replaces physical resistors with an electronic circuit implementation using MOS transistors configured as a positive impedance converter. This substitution allows achieving high impedance values (≥1 MΩ, up to 1 GΩ) without the proportional increase in stray capacitance that plagues physical resistors, as the impedance is synthesized electronically rather than physically realized.
Solution Approach 2:
The patent changes the fundamental parameter realization method from physical resistance to electronic impedance synthesis. By using MOS transistors in a positive impedance converter configuration, the impedance value becomes a derived parameter controlled by transistor dimensions and bias currents rather than a physical property, enabling high impedance with minimal stray capacitance.
2Manufacturing precision
If discrete time resistive devices with switched capacitances are used to reach high impedance values, then the impedance value increases, but the switching noise becomes too high
Solution Approach 1:
The patent implements a continuous-time impedance device using MOS transistors operating in their linear region, eliminating the need for switching operations. This continuous operation provides high impedance values without the switching noise inherent in discrete time implementations, as there are no periodic charge/discharge cycles of capacitances causing noise.
3Manufacturing precision
If other electronic devices such as long MOS transistor or feedback transconductance amplifier are used, then the impedance value increases, but the voltage dynamics becomes too low
Solution Approach 1:
The patent designs the positive impedance converter using MOS transistors biased in the linear region with appropriate current mirrors, enabling large voltage swings (from 0.3V to 1.2V) while maintaining high impedance. The dynamic operation is achieved through proper biasing and transistor sizing that allows the output voltage to vary widely without leaving the linear operating region.
Solution Approach 2:
The patent changes the operating parameters of the MOS transistors to operate in the linear region with optimized current mirrors, enabling both high impedance and large voltage dynamics. By adjusting the transistor dimensions and bias currents, the device achieves voltage swing capability that other electronic resistor implementations lack.
4Manufacturing precision
If other electronic devices are used to achieve high impedance values, then the impedance value increases, but the noise density deviates from the ideal 4 kBTR value
Solution Approach 1:
The patent replaces physical resistors with an electronic implementation that carefully manages noise sources. The positive impedance converter using MOS transistors in the linear region produces thermal noise that closely matches the ideal 4 kBTR spectrum, unlike switching-based or other electronic implementations that introduce additional noise mechanisms.
5Manufacturing precision
If other electronic devices are used to achieve high impedance values, then the impedance value increases, but the stray capacitance becomes too high
Solution Approach 1:
The patent replaces physical resistors with an electronic circuit implementation that inherently has minimal stray capacitance. The MOS transistor-based positive impedance converter achieves high impedance values without the large physical dimensions required by physical resistors, resulting in stray capacitance that is negligible compared to the integration capacitance.
6Manufacturing precision
If physical resistors are used to achieve high impedance values, then the impedance value increases, but the area occupied becomes too large
Solution Approach 1:
The patent replaces physical resistors with a compact electronic circuit using MOS transistors configured as a positive impedance converter. This substitution achieves high impedance values (≥1 MΩ, up to 1 GΩ) in a minimal area, as the impedance is synthesized electronically rather than requiring large physical resistor structures.
Solution Approach 2:
The patent changes from physical resistance realization to electronic impedance synthesis using MOS transistors. By controlling transistor dimensions and bias currents, high impedance values are achieved with minimal area occupation, overcoming the area limitation of physical resistors.
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 device achieves impedance values up to 1 GΩ or higher with low stray capacitance, thermal noise equivalent to physical resistors, and efficient area and power consumption, while maintaining linearity and frequency operation from DC.
Implementation Method 1
a first circuit able to, or configured to, apply between the two second terminals a voltage substantially equal to that between the two first terminals
Implementation Method 2
a second circuit able to, or configured to, flow between the two second terminals a second current the value of which corresponds to a fraction of a first current for flowing in the reference resistor between the two first terminals
Implementation Method 3
the impedance value of the reference resistor is modified by virtue of the second current imposed between the two second terminals and the value of which corresponds to a fraction of that of the first current
Data Source
AI summary
An electronic device includes a reference resistor, two first terminals between which the reference resistor is connected, and two second terminals between which a modified impedance value of the reference resistor is intended to be obtained. The electronic device also includes a first circuit that applies between the two second terminals a voltage substantially equal to that between the two first terminals, and a second circuit that flows between the two second terminals a second current the value of which corresponds to a fraction of a first current for flowing in the reference resistor between the two first terminals.