Posted on Jan 17, 2013 9438
The primary advantage of this circuit, when compared to other comparators, is its ability to latch after the input has reached a predetermined threshold level. When the input exceeds the threshold level, the LM311N output increases. This transition enables the strobe input, preventing the output from falling low. A high-level voltage on the reset input will tum off Q1, thereby removing the supply voltage from the open collector output of the LM311N.
With no supply to the strobe input, the latch condition is removed and the output is again allowed to follow the input excursions. The LM311N will operate with a wide variety of supply voltage levels, ranging from dual Â± 15 V to a single 5 V level that provides compatibility with digital IC logic. If more than one latch is used with a common reset, all the pull-up resistors may be connected to Q1"s collector.