PCB News - EMC design method of analog circuit

[1]. Optimal circuit
For example, design low-noise circuits, reduce bandwidth, suppress interference transmission, balance input, suppress interference, and select high-quality power supplies.

[2]. Use the following signal filters

--Low-pass filter When the frequency band of the interference signal is farther than the frequency band of the useful signal, a low-pass filter can be used to filter out the interference signal.

The signal-to-noise ratio σL of the RC low-pass filter is

ΣL={1+[SRL/(R+RL )]2}1/2(21)

where: S=2лfRC;

F is the frequency of the signal (Hz);

R is the resistance of the filter (Ω);

RL is the resistance of the load (Ω);

C is the capacitance of the filter (F);

--High-pass filter When the frequency band of the interference signal is farther than the frequency band of the useful signal, a high-pass filter can be used to filter out the interference signal.

The signal-to-noise ratio σG of the RC low-pass filter is

ΣG=[S2/(1+S2)]1/2(22)

where: S=2лfRC;

F is the frequency of the signal (Hz);

R is the resistance of the filter (Ω);

C is the capacitance of the filter (F);

--LC filter When the frequency band of the interference signal is higher than but close to the frequency band of the useful signal, the LC filter can be used to filter the interference signal.

The signal-to-noise ratio σY of the LC filter is (when L=CRL2)

ΣY=[(1-ω2LC)2]1/2(23)

where: ω=2лf;

F is the frequency of the signal (Hz);

RL is the resistance of the load (Ω);

C is the capacitance of the filter (F);

L is the inductance (H) of the filter.

--Gating filter When the frequency band of the interference signal is discontinuous, an LC gating filter or an RC gating filter can be applied. Among them, the LC gating filter is divided into two types: parallel resonant type and series resonant type.

The above is an introduction to the EMC design method of analog circuits. Ipcb is also provided to PCB manufacturers and PCB manufacturing technology.