| 摘要 |
An Electromagnetic Interference suppression apparatus allows common mode noise energy in signal lines to be reduced without attenuating a normal mode signal. A communication circuit has an earth terminal 3E connected to a housing 10 via a common mode impedance. At least one common mode choke 80, 81 with at least two coils is provided in the housing. One coil connects a signal terminal 8H,8J to a signal transmission wire 3H,3J; the other coil connects the earth terminal to the quasi ground surface 20 of the housing. The common mode choke causes a common mode radiant noise generated by the common mode impedance to be removed from the signal transmission wire without affecting a normal mode signal flowing through the signal wire. The communication circuit may have more than one transmission wire. In alternative embodiments ferrite beads with a plurality of holes may be used instead of the common mode chokes. Alternatively, the transmission wire may be connected to the inverting terminal of an operational amplifier and the earth terminal connected to the positive terminal through a resistor which provides a reference voltage.
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