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Digital Amplifiers Suppress Ground Interference

Edit:Guangzhou Langyuan Audio Equipment Co.Ltd   Date:Aug 22, 2017

Digital Amplifiers Suppress ground interference

Analog circuits involve weak signals, but the digital circuit threshold level is higher, the requirements of the power supply than the analog circuit lower. There are digital circuits and analog circuits in the system, the digital circuit noise will affect the analog circuit, the analog circuit of small signal indicators worse, to overcome the way is to separate the analog and digital ground.

For the low-frequency analog circuit, in addition to thickening and shortening of the ground, the circuit part of the use of a little ground is to suppress the best choice for ground interference, mainly to prevent the common impedance due to ground caused by mutual interference between components.

For high-frequency circuits and digital circuits, since the inductance effect of the ground wire will be greater, a little grounding will cause the actual ground extension and adverse effects, then take a separate ground and a little ground combination of the way.

In addition to the high-frequency circuit also consider how to suppress high-frequency radiation noise, the method is: as much as possible to reduce the ground to reduce the noise to ground impedance; full ground, that is, in addition to the transmission signal transmission line, the other part of the ground The Do not use useless large area copper foil.

The ground wire should form a loop to prevent high frequency radiation noise, but the area surrounded by the loop can not be too large to prevent the induced current when the instrument is in a strong magnetic field. But if only low-frequency circuit, you should avoid the ground loop. Digital power and analog power supply is best isolated, the ground is arranged separately, if there is A / D, only a single point here.

There is little impact in the low frequency, but it is recommended that the analog and digital ground. High frequency, through the magnetic beads to analog and digital to a little land.

If the analog ground and digital to a large area directly connected, will lead to mutual interference. There are four ways to solve this problem: 1, with a magnetic bead connection; 2, with a capacitor connection; 3, with an inductive connection; 4, with 0 ohm resistor connection.

The equivalent circuit of the magnetic bead is equivalent to the band limiting filter, only a certain frequency of the noise has a significant inhibitory effect, the use of pre-estimated frequency of noise in order to use the appropriate model. For situations where the frequency is uncertain or unpredictable, the bead does not fit.