uSupply - 100nF vs 0.1uF - Page 1
Forum section: electronics / beginners

author: poindexterity
author_rank: Contributor
timestamp: July 22, 2016, 02:06:42 pm
content: http://www.eevblog.com/files/uSupplyBenchRevC.pdfIn some places (the PWM filter), Dave uses 0.1uF denoted caps. In others (ADC input, op amp V+) he uses 100nF.Why does he use both? Is it to denote different types of capacitor? I know the op amp (decoupling?) filters should be ceramic, but don't know what type of nonpolarized cap to use in the filter. I would assume that it's Tantalum, but I don't really know.

author: ebclr
author_rank: Super Contributor
timestamp: July 22, 2016, 02:09:57 pm
content: 100nF = 0.1uF = 100KpfEverything is exactly the same value

author: poindexterity
author_rank: Contributor
timestamp: July 22, 2016, 02:11:30 pm
content: Yes, I'm aware of SI notation.My question is this: Why does Dave use both notations on the same schematic? Why not use 0.1uF everywhere or 100nF everywhere?

author: ebclr
author_rank: Super Contributor
timestamp: July 22, 2016, 02:21:43 pm
content: It's because he is Australian

author: poindexterity
author_rank: Contributor
timestamp: July 22, 2016, 02:48:04 pm
content: So you're implying that he doesn't intend anything by the different markings. I can use the same ceramic capacitors in all places that are nonpolarized 0.1uF and 100nF, is that correct?

author: ebclr
author_rank: Super Contributor
timestamp: July 22, 2016, 03:17:03 pm
content: No, polarized capacitor normally have a + on one side off the schematic,https://commons.wikimedia.org/wiki/File:Polarized_capacitor_symbol.png

author: poindexterity
author_rank: Contributor
timestamp: July 22, 2016, 03:46:22 pm
content: I don't mean to nitpick, but your responses consistently miss the mark. I asked:Quote from: poindexterity on July 22, 2016, 02:48:04 pmAnd you responded:Quote from: ebclr on July 22, 2016, 03:17:03 pmCan you explain how your response answers my question?

author: ZeTeX
author_rank: Frequent Contributor
timestamp: July 22, 2016, 03:51:47 pm
content: Quote from: poindexterity on July 22, 2016, 02:48:04 pmYes

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 23, 2016, 12:45:26 am
content: Laziness.I seek consistency over laziness, so I actively search out any labels that are inconsistent.I typically label capacitors as:0.1uF and up1-99nF1-999pFI do not place "0.01uF" and "10nF" simultaneously in the same design. That would be silly!Similarly, I have a preferred system for resistors (for which, a thousand is always lowercase 'k', because it's kilo, not Kelvin!) and inductors.By "typically", I allow for differences between projects, especially when I'm maintaining an existing design. Someone called a Y1 cap "2200pF"? Oh well, just make sure the rest do.Tim

author: Rerouter
author_rank: Super Contributor
timestamp: July 23, 2016, 02:07:46 am
content: for myself i am an engineering notation kind, so 0-999pF, 0-999nF, 0-X uF, so yes i will call a 2200uF cap 2200uF not 2.2mF,

author: ebclr
author_rank: Super Contributor
timestamp: July 23, 2016, 02:14:27 am
content: Just because the capacitor have the same value, does not mean they are the same capacitor, this is why you need to make a bom list, some capacitor are optimized to have a good relation volume / capacitance , others to have low esr, others to have good temperature performance, it's a real science to use the right capacitor at the right place. I doubt Dave take care to have this defined at schematic level since is impossible to differentiate all kinds off capacitor only by the symbol / value notation

author: derGoldstein
author_rank: Regular Contributor
timestamp: July 23, 2016, 04:10:08 am
content: I can think of one example that I've seen a very long time ago for this type of inconsistency, and which I'll occasionally use myself: "0.1uF" means it's a bypass cap, "100nF" means that it's anything else. I'm not at all saying that this is why it's this way here, just that it's just one reason that I've seen it done.When there are a lot of ICs on a board communicating using SPI or I2C, mixed in with all sorts of comparators and op-amps, you're going to have a ton of small capacitors, half of them probably bypass caps. To make the schematic a bit easier to read, I'd put "0.1uF" for all of the bypass caps, because that's an explicit exception to how I'd normally write that value -- "100nF". That way when I come back to that schematic a couple of years later and try to figure out why everything is laid out the way it is, I can "ignore" the bypass caps. Anyone else looking at the schematic might be annoyed at the inconsistency, but it won't interfere with them reading it.But that's just me.

author: EEVblog
author_rank: Unknown
timestamp: July 23, 2016, 07:42:16 am
content: Quote from: poindexterity on July 22, 2016, 02:11:30 pmI might have copied stuff from other older schematics.

author: Brumby
author_rank: Unknown
timestamp: July 23, 2016, 08:33:07 am
content: I can't say mixing up 0.1uF and 100nF on a circuit has ever worried me. I've even coped with 0.22uF and 220nF.

author: mrpackethead
author_rank: Super Contributor
timestamp: July 23, 2016, 09:30:42 am
content: Quote from: Rerouter on July 23, 2016, 02:07:46 amyes, i use this as well.. my notation would look like1p2F 11pF 82pF 680pF1nF 8n2F47uFResistors are tricky, because i do something bad.. 0R012 12R2 1k56 1M56

author: Brumby
author_rank: Unknown
timestamp: July 23, 2016, 12:58:54 pm
content: I can read 6k8 - but I write 6.8k. Old fashioned, but explicit.

author: timb
author_rank: Super Contributor
timestamp: July 23, 2016, 01:46:38 pm
content: Quote from: Brumby on July 23, 2016, 12:58:54 pmI was brought up with the 6.8k notation, but eventually switched to 6k8, as it's much, much clearer to read. Decimal points can get lost or misread easily. This is also why I use 100n instead of 0.1u almost exclusively.

author: StillTrying
author_rank: Super Contributor
timestamp: July 23, 2016, 02:40:46 pm
content: I use them all, 0.22u, 220n, and even 0u22, 2R2, 22R, 22K 2K2.Quote from: EEVblog on July 23, 2016, 07:42:16 amDid you copy U12A LM358, I think it's a mistake and it's inputs and output won't work up there.

author: klunkerbus
author_rank: Unknown
timestamp: July 23, 2016, 02:55:29 pm
content: At least the days of capacitors being labeled as uuF instead of pF seem to be behind us now...

author: Seekonk
author_rank: Super Contributor
timestamp: July 23, 2016, 06:32:30 pm
content: I drew a quick schematic for a beginner on a board and noted a resistor should be 10-22K. He came back the next day all pissed after it blew up in his face. He said just to be safe he used a 15 ohm. To be safe I no longer write it that way. Still not sure who was grammatically correct.