Transmission line driver having controllable rise and fall times with variable output low and minimal on/off delay

摘要

A driver for providing binary signals from a data system to a transmission line includes a data input node and an output transistor coupled between a data output node and ground. The output transistor has a gate, a source and a corresponding gate-source voltage therebetween. A first transistor is coupled to the gate of the output transistor and is responsive to signals applied to the input node. It conducts a discharge current from the gate of the output transistor for discharging the gate of the output transistor to reduce its gate-source voltage. A clamping circuit clamps the gate-source voltage of the output transistor to a first voltage level above ground to prevent the discharge current from reducing the, gate-source voltage of the output transistor to ground. In another embodiment, a supply voltage dependent current source adjusts a gate voltage of a second transistor in response to an increase in the supply voltage so that an initial charging current is maintained at a relatively constant level in response to increases in the supply voltage. A method of reducing a turn-on delay of an output transistor of a transmission line driver is also disclosed.