Patent ID: 6441653
Filing Date: 2002-08-27
Classification: H03K

Abstract:
A CMOS output driver circuit comprising:a single pull up output transistor connected between a first supply terminal and an output terminal, the pull up output transistor having a control terminal; a single pull down output transistor connected between a second supply terminal and the output terminal, the pull down output transistor having a control terminal; and an input terminal for receiving an input signal and connected to a pull up slew rate control circuit and to a pull down slew rate control circuit; the pull up slew rate control circuit forming a DC feedback path between the output terminal and the pull up output transistor control terminal and operative to generate and provide a variable control voltage to the pull up output transistor control terminal; the pull down slew rate control circuit forming a DC feedback path between the output terminal and the pull down output transistor control terminal and operative to generate and provide a variable control voltage to the pull down output transistor control terminal, wherein the pull up slew rate control circuit comprises a CMOS transistor and a resistor voltage divider, the CMOS transistor responsive to changes in output terminal voltage such that its resistance changes to vary a resistance ratio associated with the resistor voltage divider and such that the variable control voltage to the pull up output transistor control terminal changes with the changes in the resistance ratio.