Variable Resistor with Exponential Resistance for Analog Gain Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing variable resistors used in analog amplifiers and filters face challenges in precisely controlling cutoff frequency and gain, especially in high frequency bands, due to limitations in resistance variation and significant quantization errors, leading to inaccuracies in gain and cutoff frequency control.
Innovation Solution
A variable resistor design that increases resistance exponentially with the control code, using a series connection of resistors and switches, allowing for precise control of cutoff frequency and gain by adjusting the connection states of switches in a complementary manner, minimizing parasitic resistance influence and simplifying the logical circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a binary variable resistor is used with linear resistance variation, then the circuit structure is simple, but quantization errors increase significantly in high frequency bands leading to inaccurate gain and cutoff frequency control
Solution Approach 1:
The patent changes the resistance variation pattern from linear to exponential with respect to the control code. This parameter change in the resistance characteristic allows for finer resolution in high frequency bands where precise control is most needed, while maintaining a relatively simple circuit structure using standard resistor and switch components.
Solution Approach 2:
The variable resistor is divided into multiple segments with different resistance values that are selectively connected based on the control code. This segmentation allows the resistance to vary exponentially across different control code ranges, reducing quantization errors in high frequency bands while keeping each individual segment simple.
2Measurement precision
If resistance values are increased to improve high frequency control, then cutoff frequency accuracy improves, but parasitic resistance influence increases
Solution Approach 1:
The patent uses partial action by selectively connecting only the necessary resistor segments based on the control code and frequency band. This avoids using excessive resistance values that would amplify parasitic effects, while still achieving sufficient resolution in high frequency bands by combining smaller resistance segments in specific configurations.
3Measurement precision
If exponential resistance variation is implemented, then quantization errors are reduced and control accuracy is improved, but the logical circuit complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-configuring the resistor segments with specific resistance values that correspond to exponential progression. This preliminary design of the resistance ladder allows the control logic to simply select pre-calculated resistance values, reducing the complexity of real-time calculations while achieving exponential resistance variation.
Data Source
Figure 1~3
Figure 4~6
Figure 7~8
AI summary
Provided is an analog amplifier for amplifying an analog signal and an analog filter, and in particular, an apparatus and method for controlling gain and cutoff frequency of the variable gain amplifier and the variable cutoff frequency filter that is capable of changing the gain and cutoff frequency. The variable resister includes a plurality of resister segments in the variable resister and, when a plurality of resistance candidates for the variable resister are arranged in order of size, the resistance candidates form a geometric series.