On Tuesday, January 24, 2023 at 5:36:47 PM UTC-8, Phil Hobbs wrote:> whit3rd wrote: > > On Tuesday, January 24, 2023 at 12:47:09 PM UTC-8, Phil Hobbs wrote: > > > >> It's already not that easy to get less than 0.1 pF to ground from a PCB > >> pad, let alone a trace. > > > > Yeah, but the usual trim techniques still work; RG174 is 30 pF/foot, > > so you can get your 0.1 pf by soldering a short length onto the board, and then > > with flush nippers, cut it off. > I invite you to try getting the fringing capacitance of an actual piece > of RG-174, connected to a circuit, to be that low. Show your work. ;) > > (The capacitance per unit length only applies when the fringing > capacitance is negligible.)But, because this is a trimming technique, there's an end correction BEFORE the snip as well as after. At least, there is until the two ends of the cable coincide... I'm not concerned with high frequencies much, so I might apply a negative capacitor first, swamp it with the long-RG174 trimmer, then trim down to get near zero. Negative impedance converter, you know... <https://wiki.analog.com/university/courses/electronics/text/chapter-4>
smallest 0603 cap
Started by ●January 24, 2023
Reply by ●January 24, 20232023-01-24
Reply by ●January 25, 20232023-01-25
On a sunny day (Tue, 24 Jan 2023 10:37:01 -0800) it happened John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote in <n390th9l7dkb25tai5g3aj4cesoe6n0u5u@4ax.com>:>I need a tiny cap. > >This one is interesting > >https://www.mouser.com/ProductDetail/Walsin/RF03N0R1B100CT?qs=sGAEpiMZZMvsSlwiRhF8qtsBU8Zhqm2Ra%2Fa5698GTEQZP2uSIBTS%2FQ%3D%3DLOL looks like a type by them value .1 pF tolerane .1 pF multilayer??? LOL likely 100 nF! At 10V must be!>Below 0.1 pF, maybe I can use a 10 meg resistor, which is around 0.04 >pF. Maybe a couple in series? Maybe a network? > > > >
Reply by ●January 25, 20232023-01-25
On a sunny day (Tue, 24 Jan 2023 11:17:06 -0800) it happened John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote in <o5b0thlfg6oiep66l7om8tcnns6hldcbfq@4ax.com>:>On Tue, 24 Jan 2023 13:41:52 -0500, Phil Hobbs ><pcdhSpamMeSenseless@electrooptical.net> wrote: > >>John Larkin wrote: >>> I need a tiny cap. >>> >>> This one is interesting >>> >>> >>> https://www.mouser.com/ProductDetail/Walsin/RF03N0R1B100CT?qs=sGAEpiMZZMvsSlwiRhF8qtsBU8Zhqm2Ra%2Fa5698GTEQZP2uSIBTS%2FQ%3D%3D >>> >>> Below 0.1 pF, maybe I can use a 10 meg resistor, which is around 0.04 >>> pF. Maybe a couple in series? Maybe a network? >>> >>> >>> >> >>I have some 0.1 pF caps in stock too, primarily for adjusting the >>transfer functions of high-Z TIAs. >> >>You could maybe make a poor man's 3-terminal cap using two of those in >>series--the capacitance to ground from the midpoint would reduce the >>end-to-end capacitance. >> >>Cheers >> >>Phil Hobbs > >One end of my cap will be ground already. > >I could just use PCB capacitance, but that's hard to tune. I'd just >have to get it right first try.Bended wire, twisted wire... done it.
Reply by ●January 25, 20232023-01-25
On a sunny day (Tue, 24 Jan 2023 10:37:01 -0800) it happened John Larkin <jlarkin@highlandSNIPMEtechnology.com> wrote in <n390th9l7dkb25tai5g3aj4cesoe6n0u5u@4ax.com>:>I need a tiny cap. > >This one is interesting > >https://www.mouser.com/ProductDetail/Walsin/RF03N0R1B100CT?qs=sGAEpiMZZMvsSlwiRhF8qtsBU8Zhqm2Ra%2Fa5698GTEQZP2uSIBTS%2FQ%3D%3DI wrote:>LOL looks like a type by them >value .1 pF >tolerane .1 pF >multilayer??? >LOL > >likely 100 nF! >At 10V must be!So, even if it is really .1 pF the capacitance between the soldering masses at the ends will change that! It seems that sort of stuff (and I joked about that a while back here) is sold to clueless Spice users who never build a RF circuit and are now looking for .1 pF ??? SMDs How many THz and what sort of peeseebee they use? What a crap world of snake oil sellers Reminds me of the F35, likely also spice designed... My predictions come true, US military now goes for nuculear space propulsion, pick up where they left in the sixties.... https://www.rt.com/news/570435-nasa-darpa-nuclear-mars/ Well, nothing to worry about, anything metal floating next to it will detune its .001 pF peeseebees. If they even can get it of the ground.>Below 0.1 pF, maybe I can use a 10 meg resistor, which is around 0.04 >pF. Maybe a couple in series? Maybe a network?2 drops of solder.. add more when needed, better is to design a circuit that does not need .1 pF caps. o o - - ============== //// 0 0 / <0> ^ | cookie
Reply by ●January 25, 20232023-01-25
On Wednesday, January 25, 2023 at 12:49:32 AM UTC-5, Jan Panteltje wrote:> On a sunny day (Tue, 24 Jan 2023 10:37:01 -0800) it happened John Larkin > <jla...@highlandSNIPMEtechnology.com> wrote in > <n390th9l7dkb25tai...@4ax.com>: > >I need a tiny cap. > > > >This one is interesting > > > >https://www.mouser.com/ProductDetail/Walsin/RF03N0R1B100CT?qs=sGAEpiMZZMvsSlwiRhF8qtsBU8Zhqm2Ra%2Fa5698GTEQZP2uSIBTS%2FQ%3D%3D > LOL looks like a type by them > value .1 pF > tolerane .1 pF > multilayer??? > LOL > > likely 100 nF! > At 10V must be!LOL! But the part number matches a 0.1pF, ±0.1pF cap. So they can ship you an empty reel and claim they are within tolerance! No need for multilayer... no need for any layers!! The un-capacitor! A friend pointed out once that zero ohm resistors had amazingly tight tolerances, considering they were specified as ±10%, which would be ±0 ohms! That's a tough spec to meet. In fact, impossible. -- Rick C. + Get 1,000 miles of free Supercharging + Tesla referral code - https://ts.la/richard11209
Reply by ●January 25, 20232023-01-25
On Wednesday, January 25, 2023 at 12:52:24 AM UTC-5, Jan Panteltje wrote:> On a sunny day (Tue, 24 Jan 2023 11:17:06 -0800) it happened John Larkin > <jla...@highlandSNIPMEtechnology.com> wrote in > <o5b0thlfg6oiep66l...@4ax.com>: > >On Tue, 24 Jan 2023 13:41:52 -0500, Phil Hobbs > ><pcdhSpamM...@electrooptical.net> wrote: > > > >>John Larkin wrote: > >>> I need a tiny cap. > >>> > >>> This one is interesting > >>> > >>> > >>> https://www.mouser.com/ProductDetail/Walsin/RF03N0R1B100CT?qs=sGAEpiMZZMvsSlwiRhF8qtsBU8Zhqm2Ra%2Fa5698GTEQZP2uSIBTS%2FQ%3D%3D > >>> > >>> Below 0.1 pF, maybe I can use a 10 meg resistor, which is around 0.04 > >>> pF. Maybe a couple in series? Maybe a network? > >>> > >>> > >>> > >> > >>I have some 0.1 pF caps in stock too, primarily for adjusting the > >>transfer functions of high-Z TIAs. > >> > >>You could maybe make a poor man's 3-terminal cap using two of those in > >>series--the capacitance to ground from the midpoint would reduce the > >>end-to-end capacitance. > >> > >>Cheers > >> > >>Phil Hobbs > > > >One end of my cap will be ground already. > > > >I could just use PCB capacitance, but that's hard to tune. I'd just > >have to get it right first try. > Bended wire, twisted wire... > done it.I don't recall what gadget it was in, had such a wire indicated on the silkscreen of the circuit board. Seems a wire was soldered to the board, then bent over to create a capacitor to some other part. The board had a single through hole, and a line toward the part it was to be bent over. -- Rick C. -- Get 1,000 miles of free Supercharging -- Tesla referral code - https://ts.la/richard11209
Reply by ●January 25, 20232023-01-25
On 2023-01-25 07:57, Ricky wrote:> A friend pointed out once that zero ohm resistors had amazingly tight tolerances, considering they were specified as ±10%, which would be ±0 ohms! That's a tough spec to meet. In fact, impossible.I still have a package of 0 Ohm 5% resistors (actually, about 20 mOhm). The company switched to 1% resistors and discarded all stock of 5% reels. I saved them from the dumpster, stripped them, and repacked in 1.5x1.5" ZIP-bags. Arie
Reply by ●January 25, 20232023-01-25
On 2023-01-25, Jan Panteltje <alien@comet.invalid> wrote:> On a sunny day (Tue, 24 Jan 2023 10:37:01 -0800) it happened John Larkin ><jlarkin@highlandSNIPMEtechnology.com> wrote in ><n390th9l7dkb25tai5g3aj4cesoe6n0u5u@4ax.com>: > >>I need a tiny cap. >> >>This one is interesting >> >>https://www.mouser.com/ProductDetail/Walsin/RF03N0R1B100CT?qs=sGAEpiMZZMvsSlwiRhF8qtsBU8Zhqm2Ra%2Fa5698GTEQZP2uSIBTS%2FQ%3D%3D > > LOL looks like a type by them > value .1 pF > tolerane .1 pF > multilayer???one layer of metal, one layer of alumina, one layer of metal> LOL > > likely 100 nF! > At 10V must be!datasheet says 0.1pf -- Jasen. pǝsɹǝʌǝɹ sʇɥƃᴉɹ ll∀
Reply by ●January 25, 20232023-01-25
whit3rd wrote:> On Tuesday, January 24, 2023 at 5:36:47 PM UTC-8, Phil Hobbs wrote: >> whit3rd wrote: >>> On Tuesday, January 24, 2023 at 12:47:09 PM UTC-8, Phil Hobbs wrote: >>> >>>> It's already not that easy to get less than 0.1 pF to ground from a PCB >>>> pad, let alone a trace. >>> >>> Yeah, but the usual trim techniques still work; RG174 is 30 pF/foot, >>> so you can get your 0.1 pf by soldering a short length onto the board, and then >>> with flush nippers, cut it off. >> I invite you to try getting the fringing capacitance of an actual piece >> of RG-174, connected to a circuit, to be that low. Show your work. ;) >> >> (The capacitance per unit length only applies when the fringing >> capacitance is negligible.) > > But, because this is a trimming technique, there's an end correction BEFORE the > snip as well as after. At least, there is until the two ends of the cable coincide... > > I'm not concerned with high frequencies much, so I might apply a negative capacitor > first, swamp it with the long-RG174 trimmer, then trim down to get near zero. Negative > impedance converter, you know... > > <https://wiki.analog.com/university/courses/electronics/text/chapter-4> >Yes and no. Given invariant fringing capacitance, changing the length incrementally does give a nice predictable delta-C. Trombone line is good that way down at low frequency, for instance. This is because, in a nice long piece of coax, the E field inside is purely radial almost everywhere, and any departure from the pure TEM mode at the ends dies off exponentially, roughly as exp(-2 pi L/r), where L is the distance from the open end and r is the radius. (That's a consequence of Laplace's equation, and is also why perforated metal makes good electrostatic shielding.) However, John asked for a small absolute capacitance. A picofarad or so of end effect doesn't fit that bill. Plus when the coax gets too short, the approximation you're relying on starts getting inaccurate because (a) there are varying axial fields throughout the length of the coax, and (b) the fields at the two ends interact. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by ●January 25, 20232023-01-25
On Wed, 25 Jan 2023 05:48:33 GMT, Jan Panteltje <alien@comet.invalid> wrote:>On a sunny day (Tue, 24 Jan 2023 11:17:06 -0800) it happened John Larkin ><jlarkin@highlandSNIPMEtechnology.com> wrote in ><o5b0thlfg6oiep66l7om8tcnns6hldcbfq@4ax.com>: > >>On Tue, 24 Jan 2023 13:41:52 -0500, Phil Hobbs >><pcdhSpamMeSenseless@electrooptical.net> wrote: >> >>>John Larkin wrote: >>>> I need a tiny cap. >>>> >>>> This one is interesting >>>> >>>> >>>> https://www.mouser.com/ProductDetail/Walsin/RF03N0R1B100CT?qs=sGAEpiMZZMvsSlwiRhF8qtsBU8Zhqm2Ra%2Fa5698GTEQZP2uSIBTS%2FQ%3D%3D >>>> >>>> Below 0.1 pF, maybe I can use a 10 meg resistor, which is around 0.04 >>>> pF. Maybe a couple in series? Maybe a network? >>>> >>>> >>>> >>> >>>I have some 0.1 pF caps in stock too, primarily for adjusting the >>>transfer functions of high-Z TIAs. >>> >>>You could maybe make a poor man's 3-terminal cap using two of those in >>>series--the capacitance to ground from the midpoint would reduce the >>>end-to-end capacitance. >>> >>>Cheers >>> >>>Phil Hobbs >> >>One end of my cap will be ground already. >> >>I could just use PCB capacitance, but that's hard to tune. I'd just >>have to get it right first try. > >Bended wire, twisted wire... >done it.This used to be called a gimmick capacitor. .<https://en.wikipedia.org/wiki/Gimmick_capacitor> Joe Gwinn
