Yet another fast edge pulse generator

[Tom45]

Set the timebase to the fastest setting that still shows the full rise time. At least some scopes use the displayed trace to compute the rise time. So if the total rise takes place in less than one major division the accuracy of the reported rise time won't be all that good.

[Kibabalu]

And here the result from a Tektronix 2465B. Measurements made by using the SMA version of Leo's pulser with a rise time of approx. 28ps and a SMA to BNC adapter:

Measured Rise times inbetween 620ps and 660ps

The device clearly outreach its spec regarding the analog bandwidth. 

[Tantratron]

And here the result from a Tektronix 2465B. Measurements made by using the SMA version of Leo's pulser with a rise time of approx. 28ps and a SMA to BNC adapter

Could you share the reference or model of where you purchased the specific SMA to BNC to match the SMA gender of Leo's pulser ?

[Kibabalu]

I bought those quite cheap ones:

High Quality 4PCS SMA to BNC Kit RF Coaxial Adapter Male Female Coax Connectors

https://www.ebay.de/itm/143598904411

[Berni]

Another way to demonstrate the impact of a adapter is to add extra unnecessary adapters in between and see what it does to the rise time. If the extra adapters don't do much then that one adapter probably doesn't either.

I usually find that a cheap coax cable does more distortion to a signal than a cheep adapter. At in the high GHz digits a piece of cheep generic coax becomes a 20dB attenuator.

[Kibabalu]

The adapter usually gives an additional time delay of 20ps to 40ps, but it should not influence the rise time or give a significant attenuation.

When I find some time I'll measure it with my VNA.

[Tantratron]

Finally the BNC version was available again from stock so I've ordered one unit to Leo Bodnar from France.
Attached picture with 1st test ob my TDS784D, really amazing quality product which confirms the 1GHz bandwidth.
Will try later on my TDS794D and the strange TDS784C which I believe to rather be TDS754C (eBay seller left the 4 attenuators capacitors and modified the 4 resistors).

[artag]

I also just received one from the new stock.

I wanted it to check my DSO7000 scope out after modifying the input circuits so the BNC one was plenty fast enough (in fact, Leo's calibration showed this sample to be well beyond spec).

The first thing I tried it on was my HP53310A - I'd heard theat it could be used to make fast risetime measurements. But I got very strange results, with triggers failing  and time measurements that were for the period rather than the risetime.

I eventually realised that it's just too damn fast for the 53310A which can only resolve about 70ps - the risetime is shorter than the uncertainty in the trigger propagation.

[tggzzz]

The first thing I tried it on was my HP53310A - I'd heard theat it could be used to make fast risetime measurements. But I got very strange results, with triggers failing  and time measurements that were for the period rather than the risetime.

Setting the threshold levels is critical, and without that you measure the period. Have a look at this thread https://www.eevblog.com/forum/testgear/hpagilent-53310a-modulation-domain-analyser-frequency-time-interval-analyser/msg3196908/#msg3196908

[artag]

Albert,

Shariar did :

That is pure scope porn.

[Tantratron]

Now tested with my reconditioned TDS794D...

[cncjerry]

I don't remember if the contest here is 80/20 proximal/distal or 90/10?  Might have them reversed.  With Leo's at 80/20 I'm getting less than 30ps at 80/20.

See that's the problem with this thread, you end up with a scope (or two if I get my 8000 running) that has almost no practical purpose for verifying anything other than oc192 comm lines.  Note I said verifying because the carrier will fix it. Or you can play around looking for little bumps in coax lines...

[Alex Eisenhut]

I don't remember if the contest here is 80/20 proximal/distal or 90/10?  Might have them reversed.  With Leo's at 80/20 I'm getting less than 30ps at 80/20.

See that's the problem with this thread, you end up with a scope (or two if I get my 8000 running) that has almost no practical purpose for verifying anything other than oc192 comm lines.  Note I said verifying because the carrier will fix it. Or you can play around looking for little bumps in coax lines...

Doesn't the "o" stand for "optical"? I have an optical sampling head somewhere...

[rhb]

An old project I found and decided to investigate.

This is not in the same class as Leo's, but it turns out it achieved the goal, though I couldn't tell it at the time.  IIRC  this is the 2nd iteration, but it was 30 years ago.  I needed a <1 ns rise time step to adjust the front end of my 465 and Dumont 1062.  At the time  I thought I had failed, but I simply didn't have the tools to adjust it.  I then found a cheap Tek 106 and used that.

My 11801/SD-26 did a great job using a DL-11  I just got.  I've got an RC circuit to adjust the edge.  Initially it was OK at 2-3 ns, but a bit of twiddle and I got the rise time under 1 ns.

Have Fun!
Reg

[Mechatrommer]

man what a neck bending task, you must live somewhere 90 degree from me... btw.. reminds me that in case anyone doesnt have a FG yet, or just want to get another one as TEA collection, the synch signal of UTG962/932 can give another sub ps risetime... fwiw... https://www.eevblog.com/forum/testgear/uni-t-utg932utg962-200msas-function-arbitrary-waveform-generator-220394/msg2927402/#msg2927402

[Leo Bodnar]

I don't remember if the contest here is 80/20 proximal/distal or 90/10?  Might have them reversed.  With Leo's at 80/20 I'm getting less than 30ps at 80/20.

Digital communication industry usually uses 80/20 and normal/analogue people - 90/10.

My rule is "it's 90/10, unless explicitly stated that it's 80/20".  It's sensible, conservative and avoids spec inflation.

Cheers
Leo

[David Hess]

I don't remember if the contest here is 80/20 proximal/distal or 90/10?  Might have them reversed.  With Leo's at 80/20 I'm getting less than 30ps at 80/20.

Digital communication industry usually uses 80/20 and normal/analogue people - 90/10.

My rule is "it's 90/10, unless explicitly stated that it's 80/20".  It's sensible, conservative and avoids spec inflation.

At higher frequencies and when cable lengths are longer, transmission line "dribble-up" prevents 90/10 measurements from being useful.

[rfclown]

I just received my BNC version pulse generator. Didn't expect it so soon. Invoice 2/10, arrived in US 2/19 for $7.74 shipping. Put it on a LeCroy HDO6104 1 Gz. Rise is measuring 479 psec (10/90). Should be faster.
... Chan 2 the same. Would be more disappointed if it was my scope. I've been storing it for someone for years. At some point it migrated to the primary scope spot on my bench.

[tautech]

I just received my BNC version pulse generator. Didn't expect it so soon. Invoice 2/10, arrived in US 2/19 for $7.74 shipping. Put it on a LeCroy HDO6104 1 Gz. Rise is measuring 479 psec (10/90). Should be faster.
... Chan 2 the same. Would be more disappointed if it was my scope. I've been storing it for someone for years. At some point it migrated to the primary scope spot on my bench.

That's about right.
SDS5104X is ~400ps too.....faster scope required to resolve a faster risetime. 

[rfclown]

I just received my BNC version pulse generator. Didn't expect it so soon. Invoice 2/10, arrived in US 2/19 for $7.74 shipping. Put it on a LeCroy HDO6104 1 Gz. Rise is measuring 479 psec (10/90). Should be faster.
... Chan 2 the same. Would be more disappointed if it was my scope. I've been storing it for someone for years. At some point it migrated to the primary scope spot on my bench.

That's about right.
SDS5104X is ~400ps too.....faster scope required to resolve a faster risetime. 

Using the RT*BW=0.35 (or 0.45) I calculate 731 MHz (0.35) and 939 MHz (0.45). Both shy of 1GHz. Sampling rate of this scope is 2.5 GHz.

Measured a HP 54602B. This thing is terrible for fast one shot captures since it samples once per fortnight, but it does have the advertised BW. Stated 150 MHz; more like 200 MHz.

[2N3055]

I just received my BNC version pulse generator. Didn't expect it so soon. Invoice 2/10, arrived in US 2/19 for $7.74 shipping. Put it on a LeCroy HDO6104 1 Gz. Rise is measuring 479 psec (10/90). Should be faster.
... Chan 2 the same. Would be more disappointed if it was my scope. I've been storing it for someone for years. At some point it migrated to the primary scope spot on my bench.

That's about right.
SDS5104X is ~400ps too.....faster scope required to resolve a faster risetime. 

Using the RT*BW=0.35 (or 0.45) I calculate 731 MHz (0.35) and 939 MHz (0.45). Both shy of 1GHz. Sampling rate of this scope is 2.5 GHz.

Measured a HP 54602B. This thing is terrible for fast one shot captures since it samples once per fortnight, but it does have the advertised BW. Stated 150 MHz; more like 200 MHz.

For many years now, we have been saying that risetime of modern scope is not exactly correlated with BW with any simple ratio.
BW is determined with frequency sweep. Risetime is separate parameter and is specified independently.

Your scope has specification of 450ps 10-90% typical. Typical means it can be a bit better or worse and still be in spec. Also keep in mind risetime will vary with sensitivity and signal amplitude. At different sensitivities different combinations of attenuators and amplifier stages are switched in, making subtle changes in front end response.

Similar Siglent SDS6104H12 shows 410-415ps 10-90% risetime. So a bit better but that is with 5GSa/s.
When 2.5GSa/s is forced it shows  420-430ps. Same signal source, of course.

I would say it is just fine.

Leo ships pulsers with certificate where you can see exact risetimes and pulse shape.
Each one is individually characterized. He does fantastic job and gives superb service.
It is amazing the amount of effort and care he puts in such a simple and inexpensive device.
I wish there were more people like him in the business...
And no, no relations, just a happy customer.

[tautech]

I just received my BNC version pulse generator. Didn't expect it so soon. Invoice 2/10, arrived in US 2/19 for $7.74 shipping. Put it on a LeCroy HDO6104 1 Gz. Rise is measuring 479 psec (10/90). Should be faster.
... Chan 2 the same. Would be more disappointed if it was my scope. I've been storing it for someone for years. At some point it migrated to the primary scope spot on my bench.

That's about right.
SDS5104X is ~400ps too.....faster scope required to resolve a faster risetime. 

Using the RT*BW=0.35 (or 0.45) I calculate 731 MHz (0.35) and 939 MHz (0.45). Both shy of 1GHz. Sampling rate of this scope is 2.5 GHz.

Now with a moment to hunt out a previously captured screenshot with Leo's pulser on 5 GSa/s SDS5104X.
IIRC this pulser had a spec of 30ps risetime.

[rfclown]

I just received my BNC version pulse generator. Didn't expect it so soon. Invoice 2/10, arrived in US 2/19 for $7.74 shipping. Put it on a LeCroy HDO6104 1 Gz. Rise is measuring 479 psec (10/90). Should be faster.
... Chan 2 the same. Would be more disappointed if it was my scope. I've been storing it for someone for years. At some point it migrated to the primary scope spot on my bench.

That's about right.
SDS5104X is ~400ps too.....faster scope required to resolve a faster risetime. 

Using the RT*BW=0.35 (or 0.45) I calculate 731 MHz (0.35) and 939 MHz (0.45). Both shy of 1GHz. Sampling rate of this scope is 2.5 GHz.

Measured a HP 54602B. This thing is terrible for fast one shot captures since it samples once per fortnight, but it does have the advertised BW. Stated 150 MHz; more like 200 MHz.

For many years now, we have been saying that risetime of modern scope is not exactly correlated with BW with any simple ratio.
BW is determined with frequency sweep. Risetime is separate parameter and is specified independently.

Your scope has specification of 450ps 10-90% typical. Typical means it can be a bit better or worse and still be in spec. Also keep in mind risetime will vary with sensitivity and signal amplitude. At different sensitivities different combinations of attenuators and amplifier stages are switched in, making subtle changes in front end response.

Similar Siglent SDS6104H12 shows 410-415ps 10-90% risetime. So a bit better but that is with 5GSa/s.
When 2.5GSa/s is forced it shows  420-430ps. Same signal source, of course.

I would say it is just fine.

Leo ships pulsers with certificate where you can see exact risetimes and pulse shape.
Each one is individually characterized. He does fantastic job and gives superb service.
It is amazing the amount of effort and care he puts in such a simple and inexpensive device.
I wish there were more people like him in the business...
And no, no relations, just a happy customer.

I agree 100% about Leo. I don't really need this thing to measure my scope front ends, it was just the first thing I did when I got the pulser. I just checked the LeCroy using a sig gen, and it was down 3 dB at 930 MHz which is in line with the estimate using risetime. I have VNA and SA to verify cable losses and signal levels. I've been toying with building a fast rise pulser, and with the price Leo has for his unit it just isn't worth my time. And if I did build something like his, I couldn't measure the actual risetime. Certificate with mine says 36.34 ps rise, 30.26 ps fall. I'm also a happy customer.

[HighVoltage]

I was so happy with Leo's pulse generator, I bought two more with different connectors and all three are performing very well.

[BmaxTom]

I designed a housing for Leo's pulse generator.

Printed it with a layer height of 0.1mm and infill grid pattern with a density of 33%. I attached the cover with a little bit of super glue.