Controllable Resistive Circuit for Smooth DC Offset Cancellation
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Solution Overview
Problem
Conventional resistive circuits provide variable resistance in a discrete form, leading to poor frequency response and longer transient times, making them unreliable for DC offset cancellation.
Innovation Solution
A controllable resistive circuit comprising a transistor, capacitor, charging unit, and discharging unit, where the capacitor provides a variable voltage to control the transistor's equivalent resistance continuously, enabling smooth resistance variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional resistive circuits use discrete resistors with switches, then the circuit structure is simple, but the resistance varies only in discrete form causing poor frequency response and longer transient time
Solution Approach 1:
The patent changes the resistance parameter from discrete fixed values to continuous variable values by using a transistor's channel resistance, which can be continuously adjusted through gate voltage control. This resolves the contradiction by maintaining circuit simplicity while achieving continuous resistance variation for better frequency response.
Solution Approach 2:
The patent replaces the mechanical switch-based discrete resistance selection with an electronic field-effect transistor system where electrical voltage controls the channel resistance continuously. This substitution eliminates the discrete step changes and provides smooth resistance variation.
2Device complexity
If conventional resistive circuits use discrete resistors with switches, then the circuit structure is simple, but the transient time is longer
Solution Approach 1:
By changing from discrete to continuous resistance control, the circuit can dynamically adjust the time constant (RC) more rapidly and smoothly, reducing the transient time required for the filter to reach steady state while maintaining the simple circuit structure.
Solution Approach 2:
The patent introduces dynamic control of the resistance parameter through voltage-controlled transistor operation, allowing the circuit to adapt its time constant in real-time rather than being fixed at discrete values, thereby reducing transient response time.
3Ease of operation
If discrete variable resistance is used in switchable RC filter, then the circuit is easier to implement, but DC offset cancellation is unreliable
Solution Approach 1:
The continuous resistance variation enabled by the voltage-controlled transistor allows for precise and smooth adjustment of the RC filter's time constant, enabling reliable DC offset cancellation through continuous adaptation rather than discrete switching, while keeping the implementation straightforward.
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
Facilitates fast DC offset cancellation and smooth frequency response in filtering circuits, such as high-pass filters, with improved transient performance.
Implementation Method 1
the capacitor can provide a variable voltage which is controlled to vary continuously and smoothly to control the equivalent resistance of the transistor
Data Source
AI summary
The present invention sets forth a controllable resistive circuit which comprises a transistor, a capacitor, a charging unit and a discharging unit. The transistor is capable of providing a variable resistance which is controlled to vary continuously and smoothly. The charging and discharging units are used to respectively charge and discharge the capacitor in different periods. As a result, the capacitor can provide a variable voltage which is controlled to vary continuously and smoothly to control the equivalent resistance of the transistor during the period the capacitor is discharging. Therefore, the controllable resistive circuit in accordance with the present invention is capable of being used in any kind of circuit which requires a variable resistance varied continuously and smoothly.