Patent ID: 6118310
Filing Date: 2000-09-12
Classification: H03K

Abstract:
A variable impedance output driver for driving a signal through a signal pad on a semiconductor device, the output driver comprising:a plurality of p-channel field effect transistors (PFETs) electrically connected in parallel, wherein a source node of each of the plurality of PFETs are electrically connected together and a drain node of each of the plurality of PFETs are electrically connected together; anda plurality of n-channel field effect transistors (NFETs) electrically connected in parallel, wherein a source node of each of the plurality of NFETs are electrically connected together and a drain node of each of the plurality of NFETs are electrically connected together, and wherein the drain nodes of each of the plurality of PFETs is electrically connected with the source nodes of each of the plurality of NFETs and is further electrically coupled to the signal pad;wherein a first PFET of the plurality of PFETs has a gate node that is driven by an output of a pull-up predriver circuit and a first NFET of the plurality of NFETs has a gate node that is driven by an output of a pull-down predriver circuit, and wherein each of the remaining PFETs and NFETs have gate nodes and the pull-up and pull-down predriver circuits are driven by a calibration word generated by a control circuit.