Which ICs are Appropriate for Generating Very High Speed Pulse Waveforms - Page 1
Forum section: electronics / rf-microwave

author: strahd_von_zarovich
author_rank: Contributor
timestamp: January 16, 2023, 11:02:38 am
content: Hi everyone,I need to design a high speed pulse waveform generator. Minimum pulse width must be lower than 300ps and rise-fall time must be lower than 100ps. Delay resolution must be lower than 100ps between channels.What is the best way to do it. I worked on high speed DACs with JESD204B interface in the past. But I am not sure if it is the correct way to generate pulses.Can you tell me what kind of ICs is the best choice for this purpose?Thanks in advance.

author: jonpaul
author_rank: Super Contributor
timestamp: January 17, 2023, 12:25:41 pm
content: No need of DIY, the leo Bodnar 40ps pulser generator is the best.low cost, great specs.http://www.leobodnar.com/shop/index.php?main_page=product_info&products_id=295No connection just a satisfied user.Jon

author: joeqsmith
author_rank: Super Contributor
timestamp: January 17, 2023, 02:06:05 pm
content: What voltage levels? Maybe add a timing diagram to show more overall detail?

author: MathWizard
author_rank: Super Contributor
timestamp: January 23, 2023, 01:50:38 am
content: I've never tried to make a fast pulse or make the fastest transition possible with my parts. I've made a few multi-vibrators w/ BJT's. I should try making 1 of them as fast as I can, on a copper clad board.Pulse generator has low top-side aberrationsQuoteI might try this Jim Williams circuit with an LM393 or IDK what I'd have close to the LT1394, I might have logic chips faster than the lm393 or lm311 I have.https://www.radiolocman.com/shem/schematics.html?di=473679https://www.analog.com/media/en/technical-documentation/data-sheets/1394f.pdf

author: David Hess
author_rank: Super Contributor
timestamp: January 23, 2023, 02:42:33 pm
content: Quote from: jonpaul on January 17, 2023, 12:25:41 pmThe Leo Bodnar pulse generator uses a fast comparator from Analog Devices. The LVC logic family may be fast enough when run from a 5 volt supply. And then that leaves the fastest ECL logic families. The largest problem here is not actually the choice of logic family, but the physical packaging and layout to minimize parasitic elements.RF transistors can also do it when used to make discrete ECL logic, but unfortunately RF PNP transistors which make this easier are not longer manufactured.

author: KaneTW
author_rank: Frequent Contributor
timestamp: January 23, 2023, 02:48:30 pm
content: Quote from: strahd_von_zarovich on January 16, 2023, 11:02:38 amAny FPGA high-speed transceiver with a suitable frontend.

author: MathWizard
author_rank: Super Contributor
timestamp: January 23, 2023, 07:20:00 pm
content: So whats the rise fall time of stuff like 2.3GHz wifi stuff, or my 5.1GHz CPU ? And so what speeds are their oscillators ? I should get the calculator, but I have PCIe switches, and stuff off motherboards and GPU's. I guess they won't fit a breadboard. I never looked at any of that stuff in working operation, on a scope. Mine is 200MHz BW, I'd need one of those short ground prongs.

author: KaneTW
author_rank: Frequent Contributor
timestamp: January 23, 2023, 07:25:12 pm
content: Yeah, try two orders of magnitude more BW on the scope to see modern high speed signals accurately.

author: nctnico
author_rank: Super Contributor
timestamp: January 24, 2023, 12:52:46 am
content: Quote from: KaneTW on January 23, 2023, 02:48:30 pmI think this is a good starting point. Any FPGA a >10Gbit serialiser that allows to feed arbitrary data should do the trick. But it will be expensive.

author: TERRA Operative
author_rank: Super Contributor
timestamp: January 24, 2023, 03:07:03 am
content: I would look at the laser driver chips used for 100 Gigabit QSFP optic transcievers. They have gotta be at least a little bit fast.But for a turnkey solution, I vote +1 for the Leo Bodnar solution, another happy customer here.

author: nctnico
author_rank: Super Contributor
timestamp: January 24, 2023, 10:03:03 am
content: Quote from: TERRA Operative on January 24, 2023, 03:07:03 amThat does not meet the specs at all! Where is the 300ps pulse width??

author: Marco
author_rank: Super Contributor
timestamp: January 24, 2023, 01:28:04 pm
content: Quote from: strahd_von_zarovich on January 16, 2023, 11:02:38 amSounds like you want a multichannel digital delay generator, which is a harder problem than fast edges in most ways.I think they are generally made by combining a programmable delay line with a coarser counter. Depending on how complex the signal have to be, you might be able to implement the coarse counter with just a micro and some discrete logic (the discrete logic doing the actual counting, to avoid the jitter from the micro). Though for complex pulse trains it's probably going to have to be done with a FPGA.

author: David Hess
author_rank: Super Contributor
timestamp: January 25, 2023, 12:05:18 am
content: Quote from: TERRA Operative on January 24, 2023, 03:07:03 amI do not remember where, but I have seen some pulse generator output stages made from fast LED laser drivers.