Bad resistors
in [Design]
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From: krw on 23 Jun 2010 19:39 On Wed, 23 Jun 2010 10:13:43 -0700, John Larkin <jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >On Wed, 23 Jun 2010 09:30:03 -0700, DrParnassus ><DrParnassus(a)hereforlongtime.org> wrote: > >>On Wed, 23 Jun 2010 08:50:37 -0700, John Larkin >><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >> >>> >>>Too bad about the noise. A single 0603 100M thickfilm would have been >>>cheap and a lot less hassle. >> >> 0603 and 100M. That just sounds funny. Like simply looking at it could >>change the value between the nodes. > >Stop being silly. There is nothing special about 100 megohms. AlwaysWrong isn't being silly (that would imply a brain). He's being wrong, as always.
From: John Larkin on 23 Jun 2010 19:54 On Wed, 23 Jun 2010 18:39:23 -0500, "krw(a)att.bizzzzzzzzzzzz" <krw(a)att.bizzzzzzzzzzzz> wrote: >On Wed, 23 Jun 2010 10:13:43 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Wed, 23 Jun 2010 09:30:03 -0700, DrParnassus >><DrParnassus(a)hereforlongtime.org> wrote: >> >>>On Wed, 23 Jun 2010 08:50:37 -0700, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>> >>>>Too bad about the noise. A single 0603 100M thickfilm would have been >>>>cheap and a lot less hassle. >>> >>> 0603 and 100M. That just sounds funny. Like simply looking at it could >>>change the value between the nodes. >> >>Stop being silly. There is nothing special about 100 megohms. > >AlwaysWrong isn't being silly (that would imply a brain). He's being wrong, >as always. Oh. Right. He's afraid of numbers and afraid of resistors over a million ohms. DANGER! 2,000,000 OHMS John
From: DrParnassus on 23 Jun 2010 19:55 On Wed, 23 Jun 2010 22:08:00 GMT, Jan Panteltje <pNaonStpealmtje(a)yahoo.com> wrote: >> >>what a bunch of squabbling kids..... > >Drop dead. What is good for the goose is good for the gander. You more qualify as 'the dander' though. You're a hypocrite.
From: John Larkin on 23 Jun 2010 21:15 On Wed, 23 Jun 2010 11:01:06 -0700, DrParnassus <DrParnassus(a)hereforlongtime.org> wrote: >On Wed, 23 Jun 2010 10:12:47 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>On Wed, 23 Jun 2010 09:28:26 -0700, DrParnassus >><DrParnassus(a)hereforlongtime.org> wrote: >> >>>On Wed, 23 Jun 2010 08:50:37 -0700, John Larkin >>><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: >>> >>>>Dale says they're expensive because hardly anybody buys them. >>> >>> >>> If they have to do a lot run simply because one order triggered it, >>>they lose money if it isn't a pretty big order, and SMD has expiration >>>dates due to termination oxidation issues so they cannot simply store the >>>over-production stock either. Though I will take old parts because they >>>are usable for proto builds. >> >>As I said, they are axial RC07 types, not SMD. >> >>They do stock 22M, available from distributors at a more sensible >>price, and 33M, also distributor stock maybe. The 50M ones are >>apparently not much in demand. >> >>All *are* 1% parts. And we can measure them accurately. >> >>I need a small constant current, and it's a battle between Johnson >>noise current and shot/excess noise. It's not easy to generate a nA >>level quiet constant current. The alternative was ten 10M >>surface-mount thinfilms in series, which we don't have room for. >> >>John >> > You left out one over f. Do you even know what 1/f noise is? John
From: John Larkin on 23 Jun 2010 21:16
On Wed, 23 Jun 2010 09:45:19 -0700, DrParnassus <DrParnassus(a)hereforlongtime.org> wrote: >On Wed, 23 Jun 2010 08:50:37 -0700, John Larkin ><jjlarkin(a)highNOTlandTHIStechnologyPART.com> wrote: > >>We recently needed a 100M metal-film resistor to use in a photodiode >>TIA thing. We tested a bunch of thickfilms and all had too much excess >>noise; > > You can't just solder it in, and not clean the board completely and >start relying on test data. It being clean is the whole key. You can't >do that at the bench without a brominated solvent or hot alcohol and a >heat gun... hell... not at all. It needs to be clean. > > Working with HV and with feedback loops, etc. we established a method of >building the SMD circuit with the least leakage paths. It MUST be CLEAN. Sure, we know that. Say, did I ever tell you about the cool PCB cleaning machine we have? John |