the extremes the device sizes chosen do not yield the same resistance values but since this circuitry exploits feedback the matching scheme still works in fact the scheme has proven to work well under nominal test case conditions the target resistance values in the preferred embodiment of the present invention are as follows a the main driver 100 ohms b first increment 75 ohms c second increment 200 ohms d third increment 400 ohms these resistances provide output impedances in the range of 100 to 32 ohms as shown in table one fig4 the following is a more detailed description of each of the elements of the driver shown in driver 3 fig5 is a logic diagram of predriver 30 shown in fig3 the function of the predriver is to gate the driver enable signal with the driver input signal while still allowing the output stage to provide a high impedance signal this is accomplished by the utilization of nand gate 70 inverter 72 and nor gate 74 interconnected as shown predriver 30 ensures that a with logic input 34 1 34 only the pull up devices are turned on b with logic input 34 0 34 only the pull down devices are turned on and c in the high impedance state both the pull up and pull down devices are turned off all of which is conventional for a so called three state driver fig6 shows the output stage 32 of.