Patent ID: 8937498
Filing Date: 2015-01-20
Classification: H03H,H04L

Abstract:
1. A common mode noise reduction circuit for a transmission-signal output circuit having a first and a second output terminals configured to transmit differential signals from the first and second output terminals, the common mode noise reduction circuit comprising: a first generating circuit configured to generate electric current to input to the first output terminal or receive electric current from the first output terminal; a second generating circuit configured to generate electric current to input to the second output terminal or receive electric current from the second output terminal; and a control circuit configured to control the first and second generating circuits so that in synchronism with a drive control clock of the transmission signal output circuit, the first and second generating circuits generate current pulses to reduce common mode noise of the differential signals to be transmitted, wherein the transmission signal output circuit comprises: a first current source having a first end connected to a direct current source; a second current source having a first end connected to the ground; a first switch connected between the first output terminal and a second end of the first current source; a second switch connected between the second output terminal and the second end of the first current source: a third switch connected between the first output terminal and a second end of the second current source; a fourth switch connected between the second output terminal and the second end of the second current source; and a terminal resistor connected between the first output terminal and the second output terminal, and the transmission signal output circuit is configured to, in synchronism with the drive control clock, generate drive control signals to the first, second, third and fourth switches to power on and off at least one of the first, second, third and fourth switches to transmit the differential signals from the first and second output terminals.