Analysis of printed circuit board of the harmonic distortion prevention measures

by:A-TECH      2020-05-20
Printed circuit board is actually made up of electric linear material, namely its impedance should be constant. So, why can lead nonlinear signal within the PCB? Electronic assembly processing factory to your answer: relative to current flows through the place, is 'spatial nonlinear' PCB layout. Amplifier is from the power supply or from another source current, depending on the load signal instantaneous polarity. Current flow from the power, through the bypass capacitor, through amplifier into the load. Then, the current from the load to ground end back to the ground plane, through the bypass capacitor, back to the current power source to provide more early. Current flows through the impedance of the concept of smaller path is not correct. Current in all the different impedance and its conductivity is proportional to the path. In a ground plane, often have more than one large proportion to current flows through the low impedance path: a path connected directly to the bypass capacitor; Another before reaching the bypass capacitor, incentives for input resistance. To return current is the real reason causing the problem. Amplifier chip problem is more complicated, because it can't make the bypass capacitor to connect from all input. This is especially true for four amplifier. Four on each side of the input amplifier chip, so there is no space to place can reduce the disturbance of bypass circuit input channel. Most directly connect to four amplifier device pin. A power supply to current disturbance another importer of channel power supply voltage and current, which can lead to distortion. For example, four amplifier channel 1 ( Vs) Bypass capacitors can be directly in the near its input; And ( - - - - - - Vs) Bypass capacitors can be placed on the other side of the packaging. ( Vs) The current disturbance channel 1, while ( - - - - - - Vs) The current may be not. To return current flowing through different bypass capacitors and power itself, its size and its conductivity is proportional to the. The high frequency signal current flow back to the small bypass capacitors. Low-frequency current may be largely through the bypass capacitors. Even lower frequency current can be 'indifference' exist, all bypass flow directly back to the power supply wire. Specific application will determine which current path is more critical. Fortunately, through the adoption of common ground and to bypass capacitance of the output side, you can easily protect all current path.
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