Abstract: In a transmitter/receiver for bidirectional communication with a transmission medium, the transmitter comprises an amplifier having an input terminal for signals to be transmitted, an output stage with output terminals coupled via resistors to the transmission medium, and a negative feedback circuit connected with its input terminals to the output terminals and with its output terminal to the input terminal of the amplifier. The receiver is connected with first input terminals to the output terminals of the output stage. A current mirror is connected with its input terminal to the input terminal of the amplifier output stage and with its output terminals via resistors across a load. The load is connected across second input terminals of the receiver. The receiver is adapted to extract signals received from the transmission medium by subtracting voltages between said second input terminals from voltages between said first input terminals.

Abstract: To minimize power dissipation in a line driver (3) in a central office (CO) for driving a DSL connection to a network terminal (NT) with a predetermined maximum constellation size, the central office (CO) supplies the line driver (3) with a predetermined supply voltage during a training sequence, and transfers data with a predetermined power spectral density in all available channels. The network terminal (NT) measures the signal-to-noise ratio of each channel, and transfers information to the central office (CO) about channels having signal-to-noise ratios that enable transfer of data.

Abstract: To compensate for temperature dependent variations and process variations in surface resistance of a main resistor (R1) on a chip (1), one or more compensating resistors (R11, R12. . . R1n) can be connected in series with the first resistor (R1) via normally open switches (SR11, SR12. . . SR1n). The switches are closed to connect one or more of the compensating resistors (R11, R12. . . SR1n) in series with the main resistor (R1) in response to whether the voltage across resistors (R21, R22. . . R2n) produced on the chip (1) in the same process and proportional to the compensating resistors (R11, R12. . . R1n) is higher or lower than a fixed reference voltage (VR3).

Abstract: To compensate for temperature dependent variations and process variations in surface resistance of a main resistor (R1) on a chip (1), one or more compensating resistors (R11, R12 . . . R1n) can be connected in series with the first resistor (R1) via normally open switches (SR11, SR12 . . . SR1 n). The switches are closed to connect one or more of the compensating resistors (R11, R12 . . . R1n) in series with the main resistor (R1) in response to whether the voltage across resistors (R21, R22 . . . R2n) produced on the chip (1) in the same process and proportional to the compensating resistors (R11, R12 . . . R1n) is higher or lower than a fixed reference voltage (VR3).

Abstract: To minimize power dissipation in a line driver (3) in a central office (CO) for driving a DSL connection to a network terminal (NT) with a predetermined maximum constellation size, the central office (CO) supplies the line driver (3) with a predetermined supply voltage during a training sequence, and transfers data with a predetermined power spectral density in all available channels. The network terminal (NT) measures the signal-to-noise ratio of each channel, and transfers information to the central office (CO) about channels having signal-to-noise ratios that enable transfer of data.