Open Collector Driver With Logical Function And Breakdown Protection
Original Publication Date: 1979-Jan-01
Included in the Prior Art Database: 2005-Feb-19
The input Schottky barrier diodes serve two purposes: first, they set the threshold, yielding the desired trade off between noise margin and performance; secondly, they are used to produce the AND function at node D. The only way for node D to rise and make Tl high is if all inputs (A, B, C) are high. If one input is down, current is pulled from Rl and node D is held down, keeping T1 low. T1 supplies drive for the output device T2. The output is taken from the collector of T2, which serves to invert the signal, producing the overall AND-invert function.