Patent ID: 7598779

Claim:
Transmitter circuitry configured to produce from a pair of input signals a pair of output signals, the transmitter circuitry comprising: a first voltage source; a second voltage source; a third voltage source; differential switching circuitry operative to produce the output signals in response to the input signals; and resistor circuitry coupled to the differential switching circuitry, wherein: a voltage of the first voltage source is higher than a voltage of the third voltage source; a voltage of the second voltage source is variable; and the transmitter circuitry is operative to select between: a) a first mode in which current is conducted from the first voltage source to the third voltage source, passing through the resistor circuitry and first and second portions of the switching circuitry, and b) a second mode in which current is conducted from the second voltage source to the third voltage source, passing through a portion of the resistor circuitry and the second portion of the switching circuitry without passing through the first portion of the switching circuitry.