Power wire should has enough width to ensure low resistance and small inductance, however, value of capacitance coupling will increase accompany with its width.

On the same printed circuit board, simulated circuit and digital circuit should strictly separated by ground wire network. Moreover, reference voltage normally would be quite sensitive to vibration of ground level, so it should be separated from power wire, connect directly to the incoming interface of printed circuit board, furthermore, its ground wire should connect to an isolated and stable reference ground point of device.

Generally speaking, ground wire not only has resistance, but also inductance, additionally, it will has unknown current pass by, voltage of resistor will decrease when current pass it. CAD program has great number of defects on ground wire design of printed circuit board, because they would design all the wires as thin as they can for the sake of saving more copper size, this will bring much higher ground resistance. The most obvious way to substitute the thin ground wire is connecting all the ground wires on the copper clad layer to form a continual grounding side. Since 0.001inch (0.025mm) copper resistance is around 0.67 mΩ/in2, so under normal circumstance it is enough already.

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