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.