Poly-Resistor Impedance Circuit for Depletion Effect Linearity
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Solution Overview
Problem
Poly-resistors with high sheet resistance values exhibit unpredictable behavior due to the depletion effect, leading to non-linearity in electronic circuits, which is not effectively addressed by existing technologies.
Innovation Solution
An impedance circuit design that utilizes a controller to dynamically adjust two control voltages applied to poly-resistors based on the voltage difference across them, ensuring the control voltages are functions of the terminal voltages to suppress the depletion effect and enhance linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single resistor is used to provide a bias current, then the circuit is simple, but the linearity is poor and distortion is high
Solution Approach 1:
The single resistor is segmented into multiple resistors (first resistor, second resistor, third resistor, fourth resistor) connected in parallel. Each resistor receives a different control voltage to independently adjust its resistance, allowing the combined resistance to track the instantaneous amplitude of the input signal and improve linearity while reducing distortion.
Solution Approach 2:
The resistance values of the resistors are made dynamic by applying different control voltages (first control voltage, second control voltage, third control voltage, fourth control voltage) that vary with the instantaneous amplitude of the input signal. This dynamic adjustment allows the bias current to follow the signal envelope, improving linearity and reducing intermodulation distortion.
2Manufacturing precision
If the resistance value changes dynamically to match signal amplitude, then linearity improves, but circuit complexity increases
Solution Approach 1:
Multiple resistors are merged in parallel configuration to form a composite resistance network. The combined effect of these resistors, each controlled by different voltages derived from the same input signal, achieves dynamic resistance adjustment with improved linearity while distributing the complexity across multiple simpler components rather than requiring a single complex variable resistor.
3Stability of the object's composition
If a fixed bias current is used, then the circuit is stable, but intermodulation distortion increases
Solution Approach 1:
The resistance values of the resistors are changed as a function of the instantaneous amplitude of the input signal. By adjusting the resistance parameters dynamically based on signal conditions, the bias current adapts to match the signal envelope, maintaining stability in terms of consistent operation while reducing intermodulation distortion through amplitude-dependent adjustment.
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 proposed design significantly improves the linearity and concentration of poly-resistors by dynamically controlling the resistance, effectively mitigating the depletion effect and enhancing circuit performance.
Implementation Method 1
the depletion effect is a phenomenon in which there is unwanted variation in the threshold voltage of devices using poly-silicon as a gate material
Data Source
Figure 1~2
Figure 3~4
Figure 5A~5B
AI summary
An impedance circuit includes a first poly-resistor and a second poly-resistor. The first poly-resistor has a first terminal coupled to a first node, and a second terminal coupled to a second node. The second poly-resistor has a first terminal coupled to the first node, and a second terminal coupled to the second node. The resistance between the first terminal and the second terminal of the first poly-resistor is determined according to a first control voltage. The resistance between the first terminal and the second terminal of the second poly-resistor is determined according to a second control voltage. The first control voltage and the second control voltage are determined according to a first voltage at the first node and a second voltage at the second node.