CMOS driver circuit having reduced switching noise

In a driver circuit, high- and low-impedance drive means (26 and 28 respectively) operate in parallel to effect a desired output transition. Adaptive control means 32 respond to a threshold value of the output signal (VO) and turn off the low-impedance drive means in the course of the output transition. The low initial output impedance of the driver circuit effects rapid charging of a line capacitance CL, while toward the end of the output transition the higher output impedance of the driver circuit more closely matches the input impedance ZL of a load circuit. This higher impedance dampens ringing and thereby reduces induced supply line noise which is conventionally associated with high-speed driver circuits.