Push-Pull Driver Enhancement Using Collector-To-Substrate Capacitance
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
This article describes a push-pull driver in which a discontinuity in the voltage waveform of the output of the driver is eliminated and a delay improvement is realized. The push-pull driver includes a current switch emitter follower (CSEF) with the pull-up output device tied to the in-phase side of the switch, and the pull-down device tied to the out-of-phase side. Note the longer path from the switch for the pull-down device. During a falling transition on the output, the pull-up device will turn off before the pull-down device turns on to continue to bring the output node low. This condition is a direct result of the difference in path length to the output device. The output node flattens during the time when neither output device is on, producing a discontinuity.