circuit to "or" two NIM signals

[swaroopsb]

I have to make a circuit which will input two NIM (fast) signals from two chenneltron detector the output will be OR of these two input. one way is to convert these NIM levels to ttl level then using a fast comperator to OR these ttl and finally convert them to NIM. but this will be slow... can some one suggest some circuit .... thanks

 

[alec_t]

I have no idea what NIM signals or chenneltron detectors are, but the simplest way to OR two pulse signals of the same polarity is with a diode OR circuit (2 diodes + 1 resistor). Suitable choice of component values and layout should provide a very fast response.

 

[crutschow]

According to my information, a NIM (Nuclear Instrument Module) signal goes between a nominal -0.9V (logic 1) and 0V (logic 0) so a diode OR circuit won't work well.

What is the speed and risetime of the signals? How much degradation of this can you tolerate? Is propagation delay critical?

 

[alec_t]

signal goes between a nominal -0.9V (logic 1) and 0V (logic 0) so a diode OR circuit won't work well.

Use germanium diodes?

 

[carbonzit]

I have no idea what NIM signals or chenneltron detectors are, [...]

I think it's a misspelling of a trade name. Try searching for "Channeltron" instead. You'll get hits like this. Appears to be a brand of electron multipliers (which I really don't know what are). Seems to have something to do with mass spectrometry or some such. Pretty esoteric stuff.

 

[crutschow]

Use germanium diodes?

That would still cut the signal voltage in half more or less.

 

[squishy36]

NIM stuff is typically fast risetimes and short pulses and often comes from nuclear counting instrumentation (so nuclear folks have been sticking their instrumentation in NIM bins for 40-50 years at least). I haven't messed with this stuff in 40+ years (and I didn't do any electronics with it then), but I can say that it will require some high speed techniques (use ECL?). OP, if you want to get help, you'd better specify your problem's conditions carefully like crutschow asked about...

 

[swaroopsb]

Yes...... the NIM signal is very fast i.e. rise time is around 1 or 2 nano sec. the shape is also critical as it is to be used for Time of Flight application. I am not sure how much destortion is allowed, but i will be using CFD (constant fraction discriminator) so amplitude does not matter much. ... thanks

 

[alec_t]

One of these?

http://www.phillipsscientific.com/preview/752pre.htm