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A single 12-V supply ADSL line driver capable of delivering 20.4 dBm into a 100-Ω load with a crest factor of 5.3 is described. Additionally, a theoretical power consumption derivation of several classes of amplifiers driving discrete multitone (DMT) waveforms is presented. A prototype of the driver was fabricated in a high-voltage bipolar process and evaluated in both pure analog and system environments. This driver achieves 18 V of ac swing on a single supply of 12 V dc. This is achieved by combining internal circuitry with external Schottky diodes and capacitors to modulate internal supplies to 24 V during high crest factor signal processing. The total power consumption is 672 mW when driving a resistive load and 684 mW when driving 8.16 Mb/s down a 6-kft line at a bit error rate of less than 1 e-07 in a full reference design.