| 摘要 |
A low capacitance overvoltage protection circuit ( 80 ) provides protection to a communication line ( 12, 14 ). A diode bridge ( 46 ) is connected to the communication line ( 12, 14 ) so that overvoltages of both polarities pass through an overvoltage protection device ( 44 ) in one direction. A bias voltage supply 48 applies a bias voltage across a semiconductor overvoltage protection device ( 44 ) through isolation resistors ( 64, 66 ) to make the capacitance of the device ( 44 ) independent of changes in communication line voltages. When line voltages exceed the magnitude of the bias voltage, a blocking diode ( 82 ) prevents current from flowing through the bias voltage supply ( 48 ) in a reverse direction.
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