The invention provides for a signal generator and related method of signal generator that is tolerant to supply voltage fluctuations and differentials. A current switch (10) is arranged to be driven and that is independent of the supply voltage. By clamping the slewing voltage at the gate of a transistor driver (M5, M6), the difference between the clamped gate voltage and the threshold turn on voltage of the driver (M5,M6) is constant with respect to the supply voltage. This causes the transition edges of the driver's output voltage to be constant with respect to the supply voltage. This technique minimizes variations in the output signal edge transitions as the supply voltage varies overvarious tolerance ranges. Because this technique increases the control of the transition edges in the output signal, it is possible to generate much slower edges and still maintain a consistent transition voltage shape with variations in the supply voltage and the symbol width.