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?
smallest 0603 cap
Started by ●January 24, 2023
Reply by ●January 24, 20232023-01-24
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 -- 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 24, 20232023-01-24
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 HobbsOne 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.
Reply by ●January 24, 20232023-01-24
John Larkin wrote:> 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.It's already not that easy to get less than 0.1 pF to ground from a PCB pad, let alone a trace. 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 24, 20232023-01-24
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.
Reply by ●January 24, 20232023-01-24
On Tuesday, January 24, 2023 at 4:10:41 PM UTC-5, 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.0.04 inches for 0.1 pf. How does that work exactly? -- Rick C. - Get 1,000 miles of free Supercharging - Tesla referral code - https://ts.la/richard11209
Reply by ●January 24, 20232023-01-24
On Tuesday, January 24, 2023 at 1:28:22 PM UTC-8, Ricky wrote:> On Tuesday, January 24, 2023 at 4:10:41 PM UTC-5, whit3rd wrote:> >... 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.> 0.04 inches for 0.1 pf. How does that work exactly?That's why it takes flush nippers. :-)
Reply by ●January 24, 20232023-01-24
On Tuesday, 24 January 2023 at 19:17:17 UTC, John Larkin wrote:> 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.Yes, but when you look at the tolerances are you really gaining much? John
Reply by ●January 24, 20232023-01-24
Am 24.01.23 um 19:41 schrieb Phil Hobbs:> 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.That's why ADS or other CAD systems have these capacitor-less capacitors with interdigitated layout models that can be tuned with a scalpell if really needed on the hardware board. A 0201 cap that swims around during soldering? -------- | --------| -----*------- *-------- | --------| --------> CheersGerhard
Reply by ●January 24, 20232023-01-24
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.) Cheers Phil Hobbs