Still yet another sample and hold

frijitz · Posted: Tue May 08, 2007 2:09 pm Post subject: Still yet another sample and hold

Here's a page describing a novel twist on the S/H concept. It's a two-part circuit: the first part fires gate and trigger signals whenever its input crosses a user-set (and voltage-controlled) threshold. The second part is a S/H fired by the trigger signal from the first part.

You can use it: (1) as a standard S/H by inputting a trigger pulse into the first section, (2) to derive gate and trigger signals from any analog signal, (3) to sample one signal based on the amplitude of another, (4) to generate randon/chaotic timing signals from continuous random/chaotic signals, (5) to generate random/chaotic voltage steps from the same, (6) to derive first return maps and Poincare sections of chaotic systems, .........

The S/H section is a high-performance design with under 5 mV/sec droop and a 30 usec charging time, allowing precise sampling at rates up to 5 kHz and more.

Circuit diagram, analysis and a demo with a chaos generator:

http://home.comcast.net/~ijfritz/ch_cir3.htm

(Apologies to Rene and his YASH circuit)

andrewF · Posted: Wed May 09, 2007 2:38 am Post subject:

hi Ian
thanks for sharing this one too.
Are you planning a PCB?
would a LM311 do for the comparator?

your sound sample sounds like those tibetan temple horns after a heady brew of the local datura tea Shocked

good for scaring off demons...or was it for attracting them?? Confused

frijitz · Posted: Wed May 09, 2007 6:35 am Post subject:

Scott Stites · Posted: Wed May 09, 2007 9:55 am Post subject:

It attracted me Maybe it's a form of strange attracter? Very Happy

IMO It's certainly different enough from any sample and hold that I've ever had to fall out of the "Yet another" category - a board would be great in my book!

Cheers,
Scott

vtl5c3 · Posted: Wed May 09, 2007 10:00 am Post subject:

The cv control over threshold is a great idea. Makes me want to revisit my old Electronotes S&Hs to see if I can modify them.

BTW, I like the pulse output too... Might be interesting if an inverted pulse out could be added for doing cascaded analog shift register type stuff, especially if you're thinking of doing a quad S&H.

Romeo

frijitz · Posted: Thu May 10, 2007 10:54 am Post subject:

vtl5c3 · Posted: Fri May 11, 2007 9:12 am Post subject:

I got the idea from the S&H in Electronotes 61. You take several S&Hs in series. The signal to be processed goes from left to right, the triggers/gates go from right to left. I think that the triggers need to be inverted between stages to delay the previous stage from triggering at the same time as the next one. Sorry if I'm not explaining it well, I'm having a hard time putting it into words. Probably best if you pull out EN 61 and read the article.

Photon · Posted: Tue Apr 01, 2008 7:14 am Post subject:

I was recently building up the pcb for this one and found that all the through holes for the transistors were a bit undersized. None of my TO-92 style 2N3904s would fit. (the 3906's fit though. curious) I tried to gently open one of the holes using a miniature drill and a pin vise and managed to tear the trace off the board. I was able to repair it luckily. I ultimately solved the problem by using some transistor sockets that I had laying around. Did anyone else have this problem or did I get a bum pcb? Or maybe my NPNs had fat leads?

in any case, I'm looking forward to finishing this one up. Very Happy

peter

andrewF · Posted: Tue Apr 01, 2008 7:20 am Post subject:

I had the same problem - fat trannie legs elephant

just soldered them onto the back of the board

frijitz · Posted: Tue Apr 01, 2008 9:24 am Post subject:

Photon · Posted: Tue Apr 01, 2008 9:50 am Post subject:

No problem, Ian. Very Happy

The transistor sockets that I used have round leads.