Hi, no, it's not quite a mailbag. Oh I guess it kind of is. There's the real stuff there waiting for the mail bag, but uh I just got something from Chris Jones thank you very much Chris uh from the AC lions in the ACT I know what this is um, it's another pulse generator uh device. he uh claims he used some fast uh logic to make a pulser and he wanted me to try it out.

Well asked if I wanted to try it out on the uh high-end Agilant scope and let's have a look at the letter hi Dave don't need any of this stuff back. however I forgot what logic family chip I used and I'd like to know what chip it is in case ever need to build another one. If you feel like doing an extreme T down after you tested, appreciate, find out what chip it is. All right, Believe the Chip's mounted upside down.

So yeah, um, below is my best guess at the circuit. I've included an SMA Cable in case you don't have one. well let's uh, give it a go. runs off 3.3 Tre um uh, 5 Vols and uh and there's nothing fancy on the schematic.

uh at all. just an input buffer. squares it up and then uh, feeds it into a four parallel uh inverter drivers from some form of 74 uh series logic family. uh, presumably it's a very very uh fast one to get the incredibly fast rise times and then and output attenuator and uh to the scope.

oh look at that you know little plastic tub. It's neat I Like that. very protective. Oh okay, here's the whole kitten.

Kaboodle Nice. All right. this is his homemade job. by the way.

it's not a uh, it's not a thing that's hooked up to. uh hey, look at this. Oh, there we go. some dead bug stuff.

Let's check this out. This will be nice, beautiful dead bug style in there on the copper, um uh sheet on the bottom. it should be uh, really nice, low, uh, inductance and it should work uh, reasonably well I Suspect Now let's get a real good closeup of the dead Bug style. Construction In here, on the uh, right hand side, there's the coax the black coax there uh coming in that's coming in from the Sig gen.

hence why uh, you know it can have like a bit of uh length on the end of it cuz it Doesn't uh, really matter signal Integrity of that's not not that critical at all, but the output is used like a rigid uh, coax. here. this is actually, you know it's it's really stiff and rigid, it's not your regular uh, coax at all and uh, it's all. and you can see the jumper wires going over there from pin to pin as required.

and uh, this really should work a treat. So um, Chris doesn't know what the chip is so um, we'll have to, uh, desolder it afterwards. he he said, uh, by all means, actually destroy the circuit and find out what chip it is cuz he doesn't recall. But of course we'll uh, we won't do that first.

we'll measure it first and uh, then we'll take it apart and see what's in there. But yeah, you can see one of the see a couple of the surface mount resistors in there all right. Now if you go to Wikipedia and uh, you look up uh Overkill you will find a picture of this set up $140,000 30 13 GHz scope and a $40,000 uh Agilant 8160 Pang Pulse Function Arbitary Noise generator I Think this might do the business now. I'm just using the Uh pulse capability of it here and look what we're getting out.

Uh, it's a rather unusual stepped waveform. Check that out. Now on the P Fang What I've set up here is a 1 MHz HZ uh frequency I'm using Uh pulse mode by the way, you can see that Uh pulse is on over there pulse with continuous. so this is all the menu related to the pulse functionality and it's spot on.

1 MHz Look at those 12 decimal places. Oh it's just brilliant. I Love it. And um, basically we're uh outputting a 3.3 volt um Peak to- Peak amplitude with a 1.65 volt offset load impedance of Uh 50 hes and uh so that should can obviously go directly into our scope without blowing it up and it'll be perfect Drive Signal for our Uh for our board here for our Pulse Gen board and uh, but the reason we're getting this peculiar waveform down here is I believe Because of this Leading Edge and trailing Edge capability here.

And of course we can set up a whole bunch of things we can set up like the by the way, the pulse width is 20 nond so it's a 1 1 MHz signal repetition with a 20 MHz uh sorry, 20 Nan second pulse and we can set up all sorts of things Leading Edge trailing Edge which we'll play with the amplitude, the offset, uh, polarity, load, impedance, frequency, coupling. We've got pattern set up as well. We can set up bit shapes and we can edit the bit waveforms. Oh man! Fantastic! I Love it! But anyway, let's go into this: Leading Edge here.

it's currently set to 50% 50% so or 10 nond. And if you have a look here at the waveform, you'll see that of course it goes sort of. You know, half the time period it goes at one ramp and the other time period it goes on another ramp. So let's see what happens here.

If we adjust our Leading Edge Leading Edge Let's adjust the Leading Edge here. that's 8 nond 7. he look at that. Beautiful.

So let's take that all the way down to 1 nond that looks like it's our fastest possible thing Leading Edge trailing Edge Look at that. So still not sure why we're getting that little little kick there that's rather, uh, rather interesting and we can wind that all the way out. But uh, you can see the power of this thing to generate any type of way for like. And we haven't even scratched the surface of this sucker really.

So I'm not sure why we getting that step there again, but we're certainly getting a nice fast input pulse. But then Boop And if you're wondering if the uh Leading Edge value we've set on our P Fang 1 nond is correct, well take a look at the rise time there and uh, you can see it's uh, there's no averaging. Of course it'll get a bit more accurate if there was some averaging on there, but it's pretty Dar Close to spot on. You wouldn't expect anything less for 180,000 bucks.

Worth a kit. Let me tell you, and let's see what happens if we adjust our pulse width. that's our 20 NS that we had and if we extend it out. Look, we get that we get that hump in there.

that camel's hump I have no idea why it's doing that and then if we go beyond, that's uh, so that's 20. Okay, and if we 19, 18, 17, 15 and when we get to 14, 13, 12 and that's 10 nond and then it does that, that's a one that's a 2 nond pulse that's as low as the P Fang will go in terms of uh, pulse width. But then there's this follow imp pulse over here. What's going on? Aha I think I figured it out.

Look at this continuous mode which is what we're using is output 1 equals Channel 1 plus Channel 2. So clearly Channel two is doing something. So if we go into Channel two aha pulse width. there we go.

And if we get our channel two and we adjust that pulse width on Channel two, ta, there it is. So Channel 2 is down to 4. NS And then we can Bingo so we can combine two different channels there that's incredibly powerful and well, I don't know. Somebody's obviously playing around with this before I had it and uh, that's what it's said to.

So um, I've got to figure out how to make the output just equal to channel one. And that's the problem with having such a powerful instrument like this is that you know, really, it's uh, um, it can do so much stuff that if you set it up incorrectly, well, you're you're pretty much uh, screwed. So um, and you know it's not like a scope where there's like an auto set button you can push. Maybe there's a reset to defaults or something like that.

Maybe I could do that. Um, but anyway. uh, let's have a look. We're in the continuous so we're in continuous menu here and uh, really? I need to uh output Channel 1 plus Channel 2 I need to change that.

Um, strobe out? What do we got? Internal threshold? trigger out? No strobe out, No trigger rout. Oh man. more options than you can poke a stick at God and we haven't even scratched the surface of this thing. No wonder it cost $440,000 and I do really like this graph mode you can pull up at any time if you're sick of looking at the numbers.

just ah, show me the wave shape. there it is. Look at that. Beautiful.

except in this case it doesn't show. Um, it doesn't match what we're getting on the scope cuz it doesn't show the second uh coupled to Channel 2. so you know I'm still trying to figure this thing out folks and bingo folks I found it of course duh, you just press the uh well the out one here brings you into the output uh menu and then down in the output menu there is. hang on, let's do it again I think I thought I had it I had an output menu here anyway I was able to switch it off and Tada we have our single pulse.

Oh beautiful. All right now we have the ability just to get a normal pulse. We got 1 nond rise and fall time so you know let's let's set it to our 20 n uh pulse there and uh, we'll see what we get out. Let's plug it in.

Uh, plug our board in Chris's little board and uh, give it a go And here's the setup. I've got an SMA to BNC adapter and a BNC um sex adapter there going straight into the scope and uh, this is what we're getting out. um let me switch the power off. Boom yeah, switch the power back on and uh, something is going on there and just had a look at his circuit again and he, of course he's got AC coupling on the output.

so let's uh, short that AC coupling cap on the output and uh, give it another try. Well the AC cing fixed it. uh of course, but um, uh, we've got the issue of uh, the P Fang is, uh, clearly do is um, outputting that higher frequency sorry the lower frequency signal there on top of the uh, high frequency 20 n a second pulse that we had in there. so we got to fix that one too and that fix was dead easy of course I Just put it to square wave mode and went, ah, be done with it.

Here we go. So here's our here is our output pulse. There's some ringing. certainly some ringing, there, some overshoot, and then some ringing so that's not that great.

But in terms of you know, if we take sort of the average rise time of this thing, we are talking 250 P seconds and uh, let's turn on some average in here. And if you want to know how to do that on this thing, it's a it's a pain in the ass to use but you go into setup, then you go into acquisition and then enable Wh. If you can get it right, you know you can either use the mouse or the touch screen. It's crazy.

Anyway, 16 averages There we go. We've cleaned up our waveform a lot and oh no, now it's hang on. Well of course it's taking. You know it doesn't know where to take that.

it takes the average of that slope there for the Uh 90% Mark for calculating the rise time. So 240, you know, almost 250 PCS there for the rise time and the four time's a bit longer. All right, what I've done now is I've taking the output uh directly from the TTL chip itself and as you can see see the uh ringing there is uh, quite pronounced as that's for a 70 KZ um signal there. by the way, that's 10 khz down to 1 khz and there there you go where obviously, um, all that funny business you see there I Love I Love that effect.

That's the average in at work. That's the 16 averages doing that. It's really, uh, really, quite fun to play with that. So clearly what we need here is a proper Uh output attenuate, a proper uh load matching to match the scope and the adapters and everything else.

It needs to be tweaked. and uh yeah. Anyway, it was fun to play with and with the Uh output cap shorted, we've clear I' I've dropped this down to a 2 khz repetitive uh signal. Okay, so you can clearly see, um, that we've got multiple uh reflection issues in here.

Here's the high frequency stuff or all in there that's at 5 nond per Division And then we've got the lower frequency stuff which is 5 micros per Division And clearly we need a proper Uh matched, fully matched output attenuator. Um, you know that's matched to our scope, input, and all our you know, the coax and the whole, the whole uh business. So you know these sort of things really need to be uh, tweaked, but that they're fun to play with. You could play with these things until the cows come home.

It's really fascina. But here you know we're talking about. you know, rise time of you know, 47? you know, 480 so it's under 500 P seconds so you know it's it's. certainly certainly doing the business in terms of uh, uh, Edge rise time and stuff like that, you just got to tweak the thing to make it work.

So anyway, might have to leave that uh to another video. but uh I H I don't know I think we should, um, at least take this thing apart and have a look at what chip it's using. So let's just try and get another closeup of this before we lift it all off. You can see the Uh corner pin on the right hand chip.

there is soldered directly down to the Uh plane down there and there's copper uh tape over the top of the Chip and you can see the wires going across and then it's got Myar on top of that or some other insulating uh wrapper and uh, really is, um, you know, quite a uh, quite a piece of work and it's going to be a shame to take it apart really. But oh well. we have to find out what chip this is. Let's lift it up and you can also see that classic Tombstone capacitor there on its side.

That's how you get really low induct and you solder it directly to the Uh copper ground plane there and and then have the wire on top of it. Awesome! Well I peeled it off and uh, there's nothing on the bottom that chip at all. So we're going to have to uh, flip over the other side and take all that copper tape off I think and it's a rather interesting uh build as you can see with the uh copper tape and then what looks like the Myar over the top and then the uh, little um, enameled wire connecting uh, the various inverters in parallel. So well, I'm going to have to snip all the enamel wire off and then uh, desol to the copper tape and lift it all off.

all right. We'll try and get this at the right angle to get it on camera. Sorry. it could be a little bit tricky to see these silk screens.

it always is. But there you go. It's a Texas Instrument 74 LV C4 A A I think it is there it is. Yep, 74 LV C4 a d date code Eh, who cares? But there you go.

Excellent. Well I hope you enjoyed that. Thank you very much. Uh Chris and if you want to, uh, build up your own one by all means, um, go for it.

give it a try and uh yeah, it's I Think it's all about the Uh getting the Uh load matching and all that right As of course is obvious with Uh signal, you know, really high speeded signal Integrity stuff like this and uh, as you can see, it doesn't have to be high speed. in terms of frequency, you know it can be a 1 KZ signal. it's all about the slew rate that Rising Edge how fast that thing is and uh yep if you don't have the correct matching on the on your transmission line and your output impedances and all that sort of stuff then or or your attenuators then you're bugged. so hope you enjoyed it.

If you want to discuss it, jump on over to the E blog uh forum and if you like it, give it a big thumbs up. Thanks Chris Catch you next time.