Output characteristics stabilization of cmos devices

Abstract

Output characteristics of CMOS chips are controlled by providing a known and stable current to a representative transistor of known relative size in the CMOS chip, and arranging the output CMOS driving transistor(s) of the chip, which are of known size relative to the representative transistor, in current mirror relationship with the representative transistor. Two primary embodiments of the invention are provided. In a first primary embodiment (I.sub.d,SAT stabilization), the representative transistor is a diode-connected transistor with a saturation current which is generated by the current source and which is also provided to drive the output transistor device(s) when it is ON. In the second primary embodiment (R.sub.ON stabilization), instead of being diode-connected, a servo is used to adjust the gate voltage of the representative device until it is greater than the drain voltage by a desired amount. In this manner, the resistance (R.sub.ON) characteristics of the representative device and hence the driving transistors are controlled. The invention has particular applicability to driving unterminated buses, and I.sub.d,SAT embodiment can be arranged to provide complementary output bus driving transistors. Because similar known and stable currents are generated on different semiconductor chips, the driving currents of the output devices of the different chips will be similar.