Patent ID: 6437611
Filing Date: 2002-08-20
Classification: H03K

Abstract:
An output driver circuit for providing an output signal at an output node experiencing a large pull-down or pull-up voltage excursion with a substantially constant output impedance, comprising:a first input transistor of a size A inputting a first input signal, the first input transistor having an output node coupled to the output node of the output driver circuit, the size of a transistor being defined as (width/length) of the transistor; a second input transistor of a size B inputting a second input signal, the second input transistor having an output node coupled to the output node of the output driver circuit; a first pair of transistors, responsive to a first control signal and the output signal, for generating a second control signal, wherein the first control signal responsive to the first input signal; a second pair of transistors, responsive to a third control signal and the output signal, for generating a fourth control signal, wherein the third control signal responsive to the second input signal; a first output transistor of a size C operative to receive the second control signal, the first output transistor having an output node coupled to the output node of the output driver circuit; and a second output transistor of a size D operative to receive the fourth control signal, the second output transistor having an output node coupled to the output node of the output driver circuit; wherein ratio of A/C and ratio of B/D are such that the substantially constant output impedance is achieved as large pull-down or pull-up voltage excursion at the output node occurs.