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Analog audio signal active low-pass filter circuit of operational amplifier in multimedia communication equipment

A low-pass filter circuit, multimedia communication technology, applied in the network using active components, electrical components, multi-terminal network and other directions, can solve the problem that the op amp is easily affected by EMI, achieve good EMI immunity performance, strengthen the system Design, reduce the effect of near-field EMI

Pending Publication Date: 2022-04-26
TAICANG T&W ELECTRONICS CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

This may be due to a technical bias that op amps are susceptible to EMI and additional measures must be taken to enhance their immunity to noise

Method used

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  • Analog audio signal active low-pass filter circuit of operational amplifier in multimedia communication equipment
  • Analog audio signal active low-pass filter circuit of operational amplifier in multimedia communication equipment
  • Analog audio signal active low-pass filter circuit of operational amplifier in multimedia communication equipment

Examples

Experimental program
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Effect test

Embodiment 1

[0044] An active low-pass filter circuit for an analog audio signal of an operational amplifier in a multimedia communication device, comprising: active filtering of differential mode noise, reduction of input common mode noise, improvement of immunity to RFI and other high-frequency EMI, Low output impedance reduces interference, simulation comparison verification, the active filtering of the differential mode noise is coupled to the DM noise in the input signal through the parasitic capacitance (CP), the combined signal and noise are controlled by a first-order active low-pass filter Receive, the low-pass cut-off frequency of the differential op amp circuit is set just above the desired signal bandwidth determined by R2 and C1, the higher frequencies are attenuated by 20dB / decade, if more attenuation is required, use a higher order active filter; the stated reduction in input common-mode noise is the noise voltage that is common at the two op-amp inputs and is not part of the...

Embodiment 2

[0046] The analog audio signal active low-pass filter circuit of the operational amplifier in the multimedia communication device described in Embodiment 1, with figure 1 Shows DM noise coupled into the input signal through parasitic capacitance (CP). The combined signal and noise are received by a first-order active low-pass filter. The low-pass cutoff frequency of the differential op amp circuit is set just above the desired signal bandwidth determined by R2 and C1. Higher frequencies are attenuated by 20dB / decade. If more attenuation is required, a higher order active filter (for example, -40 or -60dB / decade) can be used. Resistors with <1% tolerance are recommended. Also, capacitors with very good temperature coefficients (NPO, COG) and a 5% (or <5%) tolerance give the best filter performance.

[0047] The op amp provides gain and improves load carrying capability. The load is not directly connected to the RC network, but is connected through an operational amplifier ...

Embodiment 3

[0049] The analog audio signal active low-pass filter circuit of the op-amp in the multimedia communication device described in Embodiment 1, the described input common mode noise reduction, the attached figure 1 , common-mode (CM) noise sources also contribute noise at the circuit input. CM noise can be described as the noise voltage that is common (or identical) at the two op amp inputs and is not part of the expected differential-mode signal that the op amp is trying to measure or condition. CM noise can occur in a variety of ways. An example is a system where the ground reference of one circuit is at a different voltage potential than the second circuit it interfaces with. The difference in "ground" voltage can be on the order of millivolts or several volts, and can also occur at many different frequencies. These differences in voltage can cause unintended voltage drops and can interfere with the flow of current in connected circuits.

[0050] Complex communication devi...

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PUM

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Abstract

The invention relates to an analog audio signal active low-pass filter circuit of an operational amplifier in multimedia communication equipment. The circuit comprises the following components: active filtering of differential mode noise, reduction of input common mode noise, improvement of immunity to radio frequency interference (RFI) and other high-frequency electromagnetic interference (EMI), low output impedance, interference reduction and simulation comparison verification, wherein the active filtering of the differential mode noise is coupled to DM noise in an input signal through a parasitic capacitor CP; the reduction of the input common-mode noise is a common noise voltage at the input ends of the two operational amplifiers and is not a part of an expected differential-mode signal for the operational amplifiers to measure or adjust, and the improvement of the immunity to the RFI and the high-frequency EMI is that the EMI strengthened operational amplifier is used for active filtering and an external EMI / RFI filter is added to the input of the operational amplifier. The low output impedance interference reduction is the extremely low output impedance, and the simulation comparison verification is simulation performed by using a 1pF parasitic capacitor. The invention is used for the active low-pass filter circuit.

Description

Technical field: [0001] The invention relates to an active low-pass filter circuit for an analog audio signal of an operational amplifier in a multimedia communication device. Background technique: [0002] Sensitive analog circuits are often used in multimedia applications such as multi-media communications. These circuits must perform their functions in their complex electromagnetic environment while maintaining immunity to noise interference. Many of these interferences are caused by noisy circuits located nearby on the same PCB (Printed circuit board), such as multimedia fusion gateway equipment, where PON passive optical networks (Passive Optical Networks) are densely distributed on the same PCB ), LAN local area network (local area network), VOIP network voice telephone service (Voice over Internet Phone), WIFI wireless local area network, HDMI high-definition multimedia interface (High-DefinitionMultimedia Interface), audio audio and other interfaces and functional ci...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03H11/12
CPCH03H11/126
Inventor 蔡云枝
Owner TAICANG T&W ELECTRONICS CO LTD
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