High Performance Push-Pull Driver
Original Publication Date: 1985-Feb-01
Included in the Prior Art Database: 2005-Feb-18
This article describes a high speed push-pull driver circuit designed for logic and memory applications. A novel circuit technique has been used to achieve fast switching performance and high current drive capability. Fig. 1 shows the output stage of a known push-pull driver. It has current mirror open-collector for pull-down and emitter follower for pull-up. The attribute of this circuit is in its output up level, which is a VBE below VCC as compared with 2 VBE's in conventional Darlington emitter follower drivers. A limitation of this design, however, is its current drive capability. The sink current (IL) of the pull-down transistor T4 for a down-going transition is limited by the mirrored current in T2 through resistor R2.