Hi Not all semiconductor processes are created equal. In order to get things going faster you change things around. Past a point, those same changes negatively impact the leakage and 1/f noise corner. When all the changes happen, the jitter goes up. That turns it very much into a "test it and see" sort of thing. You can not just pick the device off a data sheet.
Bob On Aug 21, 2013, at 4:44 PM, Ed Palmer <ed_pal...@sasktel.net> w > Since you're looking for rise times in the low or sub nanosecond range, why > wouldn't you include any logic gates where such rise times are inherent? I > was thinking of maybe a chain of faster and faster logic gates. For example, > Potato Semiconductor - no, I'm not making that up - PO74G04A has a risetime > of < 1 ns and, if you can keep the load capacitance low enough, a maximum > input frequency of > 1 GHz. > > Always trying to learn.... > > Ed > > On 8/20/2013 11:28 PM, Bruce Griffiths wrote: >> The same analysis applies however one would probably use something like >> cascaded longtailed pairs with well defined gain (series emitter feedback) >> and the low pass filter cap connected between the collectors rather than >> opamps. >> >> Bruce >> >> Ed Palmer wrote: >>> Does anyone know if this situation would benefit from doing something >>> similar to a 'Collins Hard Limiter' i.e. instead of squaring the signal in >>> one stage, use maybe two or three cascaded stages with increasing >>> bandwidths? Normally, Collins limiters are used with beat frequencies of >>> less than 1 KHz, but maybe there's value in doing at typical time-nuts >>> frequencies. >>> >>> Any thoughts? >>> >>> Ed >>> >>> >>> On 8/20/2013 10:02 PM, Said Jackson wrote: >>>> Hi Ed, >>>> >>>> For anything up to about 150MHz try the NC74SZ04 types from National if >>>> you can find them NOS. they stopped making these years ago.. Fairchild is >>>> ok too but not as fast from what I have seen. >>>> >>>> Forgot I wrote about it in 2009. Oh boy -age kicking in. >>>> >>>> Bye, >>>> Said >>>> >>>> Sent From iPhone >>>> >>>> On Aug 20, 2013, at 20:17, Ed Palmer <ed_pal...@sasktel.net> wrote: >>>> >>>>> Hi Said, >>>>> >>>>> Yes, I saw your message from 2009 where you warned about the sine waves. >>>>> That's why I was watching for it. Thanks for the warning. I also >>>>> realized that a DC Block and a 10 db attenuator makes a very nice TTL or >>>>> CMOS to Wavecrest converter for anything except 1 PPS which would need >>>>> about 15 db. I tried an old circuit that uses an MC10116 ecl line >>>>> receiver - it's actually a dead Racal Dana 1992 counter where I'm using >>>>> the processing on the external reference input to square up the signal. >>>>> It gives me a slew rate equivalent to about a 50 MHz sine wave. It >>>>> helped a lot, but not enough. I'll try a 74AC04 and a BRS2G Differential >>>>> Line Receiver (risetime < 3ns, 400Mbps throughput). Both are in my >>>>> junkbox. >>>>> >>>>> Ed >>>>> >>>>> >>>>> On 8/20/2013 8:12 PM, Said Jackson wrote: >>>>>> Guys, >>>>>> >>>>>> The dts needs to be driven by square waves, driving them with sine waves >>>>>> gives jitter values that are displayed significantly too high due to >>>>>> trigger noise. >>>>>> >>>>>> Holzworth makes a small sine wave to square wave converter that can >>>>>> drive 50 ohms. Use a DC block and an attenuator on the cmos output to >>>>>> avoid damaging the dts inputs. You can make your own converter using a >>>>>> single fast cmos gate, resistor, and blocking cap. By using >>>>>> hand-selected gates I was able to achieve less jitter with that circuit >>>>>> than what the Holzworth box was able to achieve. >>>>>> >>>>>> Doing that conversion can bring down the measured rms jitter on a very >>>>>> good 10MHz sine wave source from 10ps+ to less than 2ps - basically at >>>>>> or below the noise floor of the dts.. Once you run at the units' noise >>>>>> floor, you know your source is quite good.. >>>>>> >>>>>> Bye, >>>>>> Said >>>>>> >>>>>> Sent From iPhone >>>>>> >>>>>> On Aug 20, 2013, at 18:51, Ed Palmer <ed_pal...@sasktel.net> wrote: >>>>>> >>>>>>> Adrian, >>>>>>> >>>>>>> I used Timelab to assess the reaction of the DTS-2077 to different sine >>>>>>> wave inputs. The differences in the noise floor are surprising. The >>>>>>> attached picture was made by taking the output of an HP 8647A >>>>>>> Synthesized Generator through a splitter, and then through different >>>>>>> lengths of cables to the inputs of the DTS-2077. The combination of >>>>>>> splitter and cable loss meant I couldn't get +7 dbm @ 1 GHz. If I >>>>>>> could have, the 1 GHz line might have been lower than it was. >>>>>>> >>>>>>> Ed > > _______________________________________________ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
