Anyone have any experience with how dual gate mosfets perform in a crystal oscillator role, at low voltages (< 3 v), at frequencies say 200 - 500 MHz?
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John Larkin Wrote in message:
NXP seems to make several with a 6 v drain to source breakdown (BF1210?) that look like they could work.
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What part did you have in mind? 3 volts sounds low for a dual-gate.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation
Wow, that's a strange part. They don't say what's inside.
-- John Larkin Highland Technology Inc www.highlandtechnology.com jlarkin at highlandtechnology dot com Precision electronic instrumentation
BF1210 comes up as "discontinued". ...Jim Thompson
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I love to cook with wine. Sometimes I even put it in the food.
Past the last-buy date on that one. "No replacement." I wonder whether they'd been asked to produce this sort of specialized device for a particular customer's special application, tried to commercialize it, and found that there wasn't sufficient demand to make it worth keeping the part active?
The BF1105R is still made (Mouser and Future have them in stock).
7-volt minimum D-S breakdown voltage, with a gate2-source threshold voltage of around 0.8 when gate-1 is at 5 volts.At $0.39 each (Mouser onesies price) it seems like an experiment would be practical :-)
Maybe use a Schottky diode output level detector to feed back to the upper gate bias?
Do you mean an oscillator that works with a 200 - 500 MHz crystal? Are there such crystals?
Some circuits in that range use a VCO operating at a high frequency, phase-locked to a lower frequency crystal oscillator.
Fred
I know that there are "mesa-etched" crystals above 100MHz, but I haven't seen one as high as 500MHz. ...Jim Thompson
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| James E.Thompson | mens |
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| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
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I love to cook with wine. Sometimes I even put it in the food.
Probably noisy. Plus their f_max is usually around 700 MHz, so they don't have a lot of gain up there, which is a problem with high overtone crystals. (Or are you using one of the fancy-schmance high fundamental ones?)
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
Looks like a long tail pair with the G2s connected together. You normally bypass those to ground anyway, so it might work pretty well for some things.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
It's pretty much not worth building your own XOs these days. Packaged oscillators are so good and cheap.
Some of the synthetic oscillators, like the Fox Xpresso and the Silabs parts, go to really high frequencies and are cheaper than you can buy the parts to make an oscillator.
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
It's asymmetric, and G2 draws current. Good thing it's obsolete.
-- John Larkin Highland Technology, Inc jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Two decades ago, the highest frequency I had seen was a 116 MHz 5th overtone crystal, but as far as I understand a lot higher frequencies are currently available.
With overtone crystals, you need a tank (LC) circuit at the required frequency, otherwise the crystal might oscillate at the fundamental frequency :-).
On a sunny day (Thu, 27 Mar 2014 09:13:24 +0200) it happened snipped-for-privacy@downunder.com wrote in :
I bought a bunch of 100 MHz oscillator modules from ebay... ebay item 261003544995
6 for 9$ free shipping, cannot make it for that... logic output, works great. At that price I would think 200 MHz must exist too:-)And sure enough: ebay 261319059458
4$49 200 MHz USAnd that was a 5 second search.
Don't those oscillator modules usually require a supply voltage of 3.3 to 5 volts to work, though?
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I looked at Mouser for the silabs parts...for a 500 MHz module they wanted 40 bucks, and it needed 3.3 volts...and it was non stock. :(
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Oscillator modules, of course, come in lots of varieties; some are PLL and locked to a quartz crystal well below the output frequency; it isn't just small-integer-multiple 'overtone' tricks that are in these modules! See
On a sunny day (Fri, 28 Mar 2014 03:28:29 -0700 (PDT)) it happened whit3rd wrote in :
Right and who cares what is in it as long as it meets specs.
The phase noise of some of those synthesized modules has to be seen to be believed.
Cheers
Phil Hobbs
-- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net
On a sunny day (Fri, 28 Mar 2014 08:38:58 -0400) it happened Phil Hobbs wrote in :
That pdf says:
Parameter Symbol Test Condition Min Typ Max Unit Phase Jitter (RMS)1 J 12 kHz to 20 MHz (OC-48) -- 0.25 0.40 ps for FOUT > 500 MHz 50 kHz to 80 MHz (OC-192) -- 0.26 0.37 ps Phase Jitter (RMS)1 J 12 kHz to 20 MHz (OC-48) -- 0.36 0.50 ps for FOUT of 125 to 500 MHz 50 kHz to 80 MHz (OC-192)2 -- 0.34 0.42 ps Phase Jitter (RMS) J 12 kHz to 20 MHz (OC-48)2 -- 0.62 -- ps for FOUT of 10 to 160 MHz CMOS Output Only 50 kHz to 20 MHz2 -- 0.61 -- ps Notes: 1. Refer to AN256 for further information.
BTW the 100 MHz from ebay is direct I think, I use it the DVB-S modulator, and the constellation is very stable, mm and a free running VCO on top of that to mix it up. But I do not have the nice equipment to check it with that you have, only this:
Sure, synthesized, I dunnit with FPGA as I posted here for GPS generation... bit of low-pass to drive the VCO, no problem.
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