Open Collector Driver Circuit
Original Publication Date: 1984-Feb-01
Included in the Prior Art Database: 2005-Feb-02
The open collector driver circuit illustrated is capable of sinking a predetermined current magnitude in the Down level. When input A is Up, the T1 emitter is biased off such that T2 must conduct, turning on T3. Output A will go Down. When input A is pulled Down, T2 will turn off such that T3 is off. Output A will be pulled Up. Schottky barrier diode (SBD) S3 is included to level shift such that an acceptable noise tolerance is established for the down-level input. Diodes D1, D2 and D3 clamp the base of T1 to provide an acceptable noise tolerance for the up-level input. Select/inhibit operation is established via transistor T4. When Z is Up, the collector of T4 is pulled Down. This pulls Down the base of T1 which cuts off any emitter current from input A during the inhibit mode of operation.