I need to implement a one-shot stage to generate a negative voltage pulse (0 to -3V) lasting around 2 usec, triggered by a TTL pin of a micro. Dual PSU (+/- 5V) available.

Been considering an LM311 connected between 0 and -5V. I got just one! of those comparators for the week end and I fear to destroy it in any uncontrolled test. Additionally I cannot see how to trigger it with a positive voltage and even more as a one shot.

Reading the datsheet got me even more confused.

Any ideas about this or any better/simpler?

 

IF you let the microprocessor handle the one-shot timing (like it's supposed to)
AND you're not real finicky about the output levels
AND not much drive is needed, this might do it

 

What is the pulse used for? What kind of current must it supply in both the hi and low states? Does it need to come from a low impedance source such as the output of a digital logic part or an LM311? If a medium impedance source work, the above circuit is a nice approach.

 

What is the pulse used for? What kind of current must it supply in both the hi and low states? Does it need to come from a low impedance source such as the output of a digital logic part or an LM311? If a medium impedance source work, the above circuit is a nice approach.

I think it could be OK. It is about 120 uA when pulling down to about -3V.