High-Order Filter Circuit Using High-Pass Path Subtraction
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Solution Overview
Problem
Conventional filters require an increased number of operational amplifiers and feedback capacitors to achieve higher order, resulting in a larger footprint and increased complexity.
Innovation Solution
A filter design that incorporates a high-pass network to enhance order without increasing the number of operational amplifiers, utilizing an operational circuit with inverse polarity input terminals and high-pass networks to perform low-pass filtering operations, allowing for higher order filtering with fewer amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the order of the filter is increased by adding more operational amplifiers, then the attenuation performance is improved, but the chip area and device complexity increase
Solution Approach 1:
The patent combines multiple filter functions (high-pass filtering and low-pass filtering) into a single operational amplifier circuit. The operational amplifier simultaneously processes both the original input signal and the high-pass filtered signal, merging what would traditionally require separate amplifier stages into one unified circuit block, thereby reducing the number of operational amplifiers needed while maintaining high-order filtering performance
Solution Approach 2:
The operational amplifier in the patent performs multiple functions: it acts as both a summing amplifier and a filtering element. The same operational amplifier processes the input signal, the high-pass filtered signal, and provides feedback control, making it a multi-functional component that replaces what would traditionally require multiple specialized amplifiers, thus reducing overall circuit complexity and chip area
2Reliability
If the order of the filter is increased by adding more operational amplifiers, then the attenuation performance is improved, but the device complexity increases
Solution Approach 1:
The patent merges the high-pass filtering function and the low-pass filtering function into a single operational amplifier circuit. By combining these functions that would traditionally require separate amplifier stages and feedback loops, the circuit complexity is reduced while maintaining the high-order filtering capability needed for superior attenuation performance
Solution Approach 2:
The operational amplifier serves multiple purposes simultaneously: it performs signal summation, high-pass filtering, low-pass filtering, and provides feedback control. This multi-functionality reduces the number of discrete components and interconnections needed, thereby simplifying the overall device complexity while achieving high-order filter performance
Data Source
AI summary
A filter is provided. The filter receives an input signal and generates an output signal according to the input signal. The filter includes an input network, a high-pass network, and an operational circuit. The first input network provides a first normal path for the input signal to generate a first normal signal. The first high-pass network provides a first high-pass path for the input signal to generate a first high-pass signal. The operational circuit has first and second input terminals. The polarity of the second input terminal is inverse to that of the first input terminal. The operational circuit receives the first normal signal by the first input terminal and the first high-pass signal by the second input terminal such that a subtraction operation is performed on the first normal signal and the first high-pass filter to accomplish a low-pass filtering operation for generating the output signal.