detect pulse of 140ns and 50mv.

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hiren.dave@bhuved.com

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Hi,

i want to detect a pulse with 140ns and 50mV amplitude. i want to design such a circuit when pulse comes pic microcontroller should get an interrupt. how can i do that?

thanks in advance...
 
You need to amplify the pulse to make it bigger - but more details are required.

I don't know how long a pulse needs to be to guarantee it triggers an interrupt?, possibly the datasheet will tell you? - if it's too short a simple pulse stretcher would be needed (but again, it depends on exactly what you're trying to do).
 
hi,
the source is photodiode.
currently i am using lm 324 / lmc6482in ic for opamp and HCF4098b pulse stretcher that can stretch a pulse. but i am not getting a pulse. is these IC are good enough ? Should i buy another one? please suggest me...
 
The LM324 is too slow for amplifying a 140nS pulse. Try a high-speed opamp.
 
On the analogue side, a simple high speed op-amp comparator will do. You bias the reference minus some from the incoming signal. 140nS catch circuit using a basic 74HC4538/74HC121 monstable is very straight forward to give an input to the PIC. Can post an LTSpice sim when I get around to it.
 
WTP Pepper said:
Let me see....Maybe from the title of the thread - detect pulse of 140ns and 50mv.
Click to expand...

Clever.
Since the OP made this statement:
hi,
the source is photodiode.
currently i am using lm 324 / lmc6482in ic for opamp and HCF4098b pulse stretcher that can stretch a pulse. but i am not getting a pulse. is these IC are good enough ? Should i buy another one? please suggest me...
Click to expand...

I am curious what photo diode outputs a 140ns pulse. What test instrument did he use to make this determination?
 
Last edited:
hi,

photodiode gives output when low power laser falls on it.i determine pulse voltage and timing with calculation. i measured big pulse in cro and according to those readings, i got this small pulse.
 
hiren.dave@bhuved.com said:
hi,

photodiode gives output when low power laser falls on it.i determine pulse voltage and timing with calculation. i measured big pulse in cro and according to those readings, i got this small pulse.
Click to expand...

I don't know of any photo diode that can operate at that speed. Please share the data sheet.
 
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