"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message news:8jfbtb1hfaceg4vl8psnv8i0i65ove62nv@4ax.com...> I just did a diff pair of BFQ18's driving a diff pair of BFQ149's > driving, well, more stuff. I was shocked that everything just > worked... no oscillations, no weirdness.Maybe you just couldn't 'hear' it. :^) On a related subject, I once built a complete type D flip-flop from CML. Just to see how fast 2N3904s can possibly go. There was too much inductance and delay in the feedback loops though (which, being fairly small signals, is analog feedback too, not hard saturated digital), and it oscillated. Oh well. ;) Tim -- Seven Transistor Labs, LLC Electrical Engineering Consultation and Contract Design Website: http://seventransistorlabs.com
Reducing SMPS noise
Started by ●September 6, 2016
Reply by ●September 11, 20162016-09-11
Reply by ●September 11, 20162016-09-11
On Sun, 11 Sep 2016 16:46:51 -0400, Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:>On 09/11/2016 04:31 PM, John Larkin wrote: >> On Sun, 11 Sep 2016 14:26:51 -0400, Phil Hobbs >> <pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>> On 09/10/2016 11:47 PM, Tim Williams wrote: >>>> "Phil Hobbs" <pcdhSpamMeSenseless@electrooptical.net> wrote in message >>>> news:fe9caa14-dc46-cd6d-70c8-efafc06fadb1@electrooptical.net... >>>>> Sometimes. Power supplies are super slow compared with signal nodes, >>>>> so you don't have to worry too much about the additional capacitance >>>>> and length of trace (i.e. antenna) due to building up a discrete RLC >>>>> network. If you're living in that world, great, but many of us aren't. >>>>> For example, the Murata 0603 beads are super nice for stabilizing >>>>> microwave transistors in baseband circuits, where they can do some >>>>> amazing things. >>>> >>>> Yeah, but you go from "power supply" to "small signal" in one paragraph. >>>> You know what I'm talking about, Phil, and I know you know better than >>>> to equate them. >>>> >>>> The whole point, that I've apparently been a complete and utter failure >>>> at communicating, over the last four posts, is that power supplies are >>>> "large signal" and small signals aren't! >>> >>> Sure thing--I was agreeing with you about power supply filters, where >>> you do have the luxury of slowness. >>> >>> >>>> People can't even read, and this is a text-only forum... sigh. >>>> >>>> >>>>> Beads are also useful insurance against board turns--you can replace >>>>> an unneeded bead with a zero ohm jumper just by changing the BOM, and >>>>> of course those are always useful for debugging since you can isolate >>>>> circuit blocks by removing them. ;) >>>> >>>> Let's just put in extra tee and pi networks of DNPs and 0-ohms on every >>>> trace ever. You'll never have to rev the board again, hell, you can use >>>> the same board for a hundred other designs just with assembly variants. ;) >>>> >>>> I try to avoid jumpers and terminators, if I can. It clutters the >>>> design, which causes real delays in layout, for customers who request >>>> 100% nodal coverage. Which is often. They have their place, but not >>>> every friggin' pin needs it. Use them prudently, not pervasively. >>> >>> Sure. I usually put a space for one in the base of every transistor >>> whose f_T > 2 GHz, and add places for extra filter components at the >>> power entry, even though I may not need them. >>> >>> Cheers >>> >>> Phil Hobbs >> >> >> I just did a diff pair of BFQ18's driving a diff pair of BFQ149's >> driving, well, more stuff. I was shocked that everything just >> worked... no oscillations, no weirdness. > >Interesting. Why cascade two pairs of 1-W-class transistors?Level translation: start near ground, shift up, shift back down.> >Cheers > >Phil HobbsI did the circuit with SOT23s, and it worked, but they got absurdly hot. Too much voltage, too much current. SOT89 is a nice little package. https://dl.dropboxusercontent.com/u/53724080/Circuits/Fast_Stuff/Fast_Level_Shifter.JPG This was too easy. Something's wrong. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
Reply by ●September 12, 20162016-09-12
On Sun, 11 Sep 2016 17:12:14 -0500, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message >news:8jfbtb1hfaceg4vl8psnv8i0i65ove62nv@4ax.com... >> I just did a diff pair of BFQ18's driving a diff pair of BFQ149's >> driving, well, more stuff. I was shocked that everything just >> worked... no oscillations, no weirdness. > >Maybe you just couldn't 'hear' it. :^) > >On a related subject, I once built a complete type D flip-flop from CML. >Just to see how fast 2N3904s can possibly go. There was too much inductance >and delay in the feedback loops though (which, being fairly small signals, >is analog feedback too, not hard saturated digital), and it oscillated. Oh >well. ;) > >TimIt just needed some ferrite beads! Or base resistors, which do pretty much the same thing. -- John Larkin Highland Technology, Inc lunatic fringe electronics
Reply by ●September 13, 20162016-09-13
On Sat, 10 Sep 2016 22:42:10 -0500, "Tim Williams" <tiwill@seventransistorlabs.com> wrote:>"John Larkin" <jjlarkin@highlandtechnology.com> wrote in message >news:c649tbdk8tot755c202ioa441fccai26sd@4ax.com... >> Several of those parts hold up well at 1 amp, and even 3 amps. > >Really? I'd love to see the VNA plots. > >TimThe data sheets have Z versus current. You seem crabby lately. -- John Larkin Highland Technology, Inc picosecond timing precision measurement jlarkin att highlandtechnology dott com http://www.highlandtechnology.com
