That works in frequency domain analysis, but I don't think that Johnson and other noise sources can appear in a transient analysis.
I actually built some time-domain voltage noise sources using random functions. I don't remember why I did that, to make jitter maybe.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
Am 12.02.19 um 16:30 schrieb John Larkin:
Yes, I wrote that in my complaints list, what Spice cannot do.
regards, Gerhard
And if it ever quits (e.g. due to a transient brownout) it won't start up again.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
You can make a .wav file of band-limited white Gaussian noise pretty easily in Octave--use the Box-Mueller method and the wavwrite() function.
LTspice reads and writes them pretty well, I believe. (I haven't done it myself.)
I expect that's how Robert Macy does his .tranoise simulations that he posted about in 2014 or thereabouts.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
I've been paying close attention to JL's fast ramp generators, CML drivers and discussions on LVDS receivers to know where to start tinkering, but I would be stumbling around, not engineering it. I'm very envious of you having enough sekrit sauce and the right test gear to do it, especially so cheaply, because I'd love to put something like that out into the maker community. But I didn't ask for details because it's your livelihood. I reckon I could stumble to 500ps without much more than what I have, and any result beyond that would be randumb luck.
So (beggar holds out his bowl), any further tips are welcome.
Clifford Heath.
I have a circuit, and a built board, for a TDR that might be in the 40 ps range. The step generator is a CML comparator, and the sampler is a fast ecl D-flop, working in slideback/single-bit mode. I never got around to making it work.
The parts are a tad expensive, but 100 ps is do-able cheap, as Phil notes. 100 ps is about as slow as you'd want to go for PCB work.
There was also a TDR student project at SF State, which I sponsored. It used an SRD for the step and a classic 2-diode sampler. One of my guys was on the team, as a student, and he may have the paper still. I'll see. After he did that, I hired him.
I also have a PowerBasic program that does targeted deconvolution, namely designs a software FIR filter that makes an ugly TDR step into a pretty one.
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
I can't post the full schematic because it belongs to the customer, and because Chester designed the delay generator part, but the speedy bits of a slightly earlier version are at
It was the first TDR I ever built, so it's not like there's that much at stake. ;)
Here's a mildly redacted version of the simulation, without the customer's device attached to the sampling line at top right.
and the measured TDR response
It works a lot better with a pHEMT like an ATF55143 at Q4. Probably one of the Mini-Circuits SAV series would be a drop-in substitute, but I haven't had the opportunity to check.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
This is a basic noise gen
Version 4 SHEET 1 880 680 WIRE 320 64 128 64 WIRE 368 64 320 64 WIRE 400 64 368 64 WIRE 128 96 128 64 WIRE 320 112 320 64 WIRE 128 208 128 176 WIRE 320 208 320 192 FLAG 128 208 0 FLAG 320 208 0 FLAG 368 64 NOISE SYMBOL bv 128 80 R0 WINDOW 0 -198 53 Left 2 WINDOW 3 -336 104 Left 2 SYMATTR InstName B1 SYMATTR Value V=random(100*time) - 0.5 SYMBOL res 304 96 R0 WINDOW 0 -59 37 Left 2 WINDOW 3 -56 73 Left 2 SYMATTR InstName R1 SYMATTR Value 1 TEXT -96 64 Left 2 !.tran 5
and this one is more gaussian, fun but kinda overkill.
Version 4 SHEET 1 1484 680 WIRE 208 64 128 64 WIRE 256 64 208 64 WIRE 416 64 336 64 WIRE 480 64 416 64 WIRE 528 64 480 64 WIRE 128 96 128 64 WIRE 416 112 416 64 WIRE 128 208 128 176 WIRE 416 208 416 176 FLAG 128 208 0 FLAG 208 64 RAW FLAG 416 208 0 FLAG 480 64 OUT SYMBOL bv 128 80 R0 WINDOW 0 34 107 Left 2 WINDOW 3 -79 203 Left 2 SYMATTR InstName B1 SYMATTR Value V= VS * ( rand(K1*time) + rand(K2*time) + rand(K3*time)
(fix the usenet line wraps)
-- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Maybe it ceases conducting ofter 0.6 ns, but the transition is not, eh, snappy.
Tunnel diodes, SRDs and the like are pretty much extinct. You can play with nonlinear transmission lines / small varicaps, I once have made some half-hearted simulations in Spice, but that resulted in nothing really usable.
You can get that
<from an Analog Devices ADCMP580, with maybe just a NE555 in front of it.
The hardware that generated this is not very noble, just resurrected it from the junk bin:
<A home-etched tiny board that has ground plane, decoupling and input terminations. For the signals that count: run them into semi rigid coax just at the device pin. The board is 0.5mm Bungard pre-sensitized FR4. If your laser printer can print it on foil, you can etch it.
And no, the Chinese boards are too thick @ 1.6mm and neither cheap nor fast if there is anything non-standard. I need just a good hour from layout in the computer to start soldering.
The pinout of ECL/CML chips or op amps is always the same; a few stamp types let you hack a pulse generator in no time:
<For TDR, get Picosecod Pulse Labs app note an3045C. Now that PSPL has been bought by TEk, the app notes are no longer on their web site, but they are still on the site of PSPL's founder. Maybe they mentioned HP all too often. Grab all of the app notes, they are worth it.
Cheers, Gerhard
Many thanks, Phil. Quite a bit more complexity in the receive amp than I'd expected. Looks like the voltages written at Q4 might be wrong -
1.66 right but 1.9V should be 1.66-Vbe or about 1V? I see why you were complaining about fast PNPs becoming EOL! You have a lot of fast stages before the T&H - not easily reducible?Clifford Heath.
I ran JL's spice and the turn-off time was 0.6ns, after it decided to start turning off.
...> from an Analog Devices ADCMP580, with maybe just a NE555 in front of it.
Or an Arduino, since you need something that can digitise the S&H value.
I get good results from toner transfer. I've done 0.6mm pin spacing.
To print on using a laser printer? Or to run controlled transmission lines at this speed?
You made the same comment in December 2017 in eevblog forums. I mirrored from his site but that one isn't there. Did it have a different number?
Clifford Heath.
Lower the 50 ohms and fiddle with the generator and the time step and it can get a lot faster. A real 1N914 won't do that.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
A fast op amp such as an ADA4817 would have worked fine for the back end, but would never have been as cheap as the discrete version. ;)
The BFT92 was replaced by a bootstrapped pair of MMBT3906es, which worked just as well in this instance. For the given application, it turned out that making the transducer cleaner was cheaper than using
70-cent pHEMTs anyway, so fortuitously they wound up with some fast NPN in place of the EOL ATF55143. IIRC the eventual performance was closer to 250 ps and the jitter was around 10 ps.For super low cost, all-discrete designs are still often a win.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Never tested toner tranfer. Here, 6/6 mil is no problem. Large black areas are worse. They take some discipline during exposure. When I need really high resolution like for microstrip filters I generate .pdf output and have a local print shop make me a film for offset printing. With that, 4/4 mil design rules are easy. That used to cost ?5 for a DIN/ISO A4 oversize page, ( abt. letter size++ , true 2400 dpi). Now that they have seen that I like it, they have double the price, but it's OK. My Altium Designer generates too small pads in .pdf when they are rounded squares. :-(
On 1.6mm FR-4, a 50 Ohm line is 120 mil or so. No way to attach that correctly to a chipscale package. Let alone a differential pair.
I had PCPway/China made some boards for me. Price was $5 for PCBway @10, so each board was just 50 cent. $20 or $25 for DHL, depending on moon phase. Ah, and $2 for Paypal. The actual work is underpaid.
The boards were excellent, but beware: methinks they make the lines wider and the spaces smaller to enhance yield. That's usually OK, but not for transmission lines. But then, there were no transmission lines.
Time was 1 day for production(they were allowed a week), 4 days for DHL for transport via HK to Germany and a good week at the Leipzig customs office, because they choose not to believe the $5 production cost for 10 pcbs. Each time. No wonder that I prefer etching it myself when I get away with 1 Layer + ground, if it's small and just a test.
Yes. Copy & paste error of mine. Application Note AN-5c "10 ps Risetime Network TDT and TDR Measurements using the PSPL 15 ps Pulse Generator and HP 50 GHz Oscilloscope" The interesting thing was the junction of generator, scope and DUT. That is normally hidden in one plug in. The app note removed some doubts.
regards, Gerhard
Have you seen my pics of the SD24 internals? I could post again.
-- John Larkin Highland Technology, Inc lunatic fringe electronics
I haven't tried your method, but other folk have, and found that most laser printers have problems fusing toner to a copper sheet - not enough heat. But you find it works ok? Perhaps the photoresist has reduced thermal conductivity.
I also like to be able to quickly make single-sided boards with solid copper backside.
Right. I haven't used those tiny packages, but generally SMD pads have some extra capacitance so I don't mind necking down the trace to meet it. A friend simulated this in the past and found that the impedance discontinuities acted like a LPF at 10GHz or so, above my max 6GHz expectations. But I must try to get some thin double-copper blanks.
OSHPark is meant to be a very good middle ground between the super cheap producers and those of better capabilities.
No worries, thanks. I must read them again.
Clifford Heath.
I'm assuming the laser printed on overhead film used to expose the pre-sensitized pcb ...
That wasn't clear to me from Gerhard's description:
"Printing on foil" sounded like printing directly on 0.5mm, but you're probably right, and it wasn't.
I never tried printing on copper because it's really hard on the sensitized drum.
I have printed on paper and transferred that to copper with an iron. The trick is getting the toner to come off the paper onto the copper. It's VERY sensitive to the type of paper used. I found certain types of photo paper worked best...but the next batch of the same paper brand/type/SKU behaved differently. The other issue is that you need very thin copper so it etches before the toner resist comes off. Not exactly a production process, but I've been able to make boards for stuff I wouldn't have been able to hook up with wires.
I also tried removing the fuser heater and transferring from paper to copper. Was never able to get the paper to the copper without smudging it.
I have too. It works badly or not at all, smudging some bits and not adhering others.
I use a (high temperature) modified laminator, properly warmed up.
I have paper which was sold for the purpose. It's consistent and has the right characteristics.
I've had no issues with the toner coming off during etch. You might need to clean your copper better so it adheres, or use more heat.
The toner can have pin-holes. For best results, laminate the special foil after removing the paper layer. The foil covers the pinholes without covering features elsewhere.
Clifford Heath.
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