| 摘要 |
PROBLEM TO BE SOLVED: To provide a line driver that has a self-tuning type output impedance and the is provided with a hybrid applicable to a communication unit where transmission and reception are simultaneously performed through the same transmission line and that can be operated in an efficient mode. SOLUTION: Each pre-driver receives a driver input signal and outputs a buffer input signal and a DC offset compensation signal. A balanced bridge hybrid is connected between a buffer output terminal and an internal node. A regulation circuit generates a regulation signal to process a hybrid output during a training mode period and to apply the processed hybrid output to an adjustable current source in each buffer. By controlling the adjustable current source with the regulation signal, the output impedance of the buffer can be made to match the characteristic impedance of a transmission line connected to the transformer secondary coil.
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