cheap precise current sources? - Page 1
Forum section: electronics / projects

author: coppercone2
author_rank: Super Contributor
timestamp: October 10, 2018, 07:45:18 pm
content: I don't normally use this word, but if you need acheapcurrent source, what are good parts?Normally I would use a precise Vref and a op-amp to make a HCP... but how about pure current sources 100uA-1mA... are there any good IC's or weird solutions I missed? Something like a REF200. For biasing transducers etc.I also looked at current output DACs before I think, but the best one was still pretty crappy compared to a discrete solution (meant for fan control or something).Are there any amazing one chip solutions for this? I do like the REF200, it makes sense when you need 2 rtd or something since its pretty stable. But can you go cheaper?

author: In Vacuo Veritas
author_rank: Frequent Contributor
timestamp: October 10, 2018, 07:48:07 pm
content: How about a NUMBER for what you consider cheap? Are we supposed to guess your budget?AD5749ACPZ

author: coppercone2
author_rank: Super Contributor
timestamp: October 10, 2018, 08:00:16 pm
content: hard to say i wanna see some parts to see if anything catches my attention with price/performance ratiojust brain storming

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 10, 2018, 08:08:22 pm
content: I like the REF200. I reckon it probably doesn't qualify as cheap though?

author: IanJ
author_rank: Unknown
timestamp: October 10, 2018, 08:15:07 pm
content: Brainstormin here also........I played with a test version of my PDVS2 and gave it an extra banana socket and a 0-2mA output (as well as the 0-10Vdc mode). If I remember correctly it's load range was something like 0 to 5kohm. It is based around the INA326 amp for the final current output drive which works pretty good.I never put it into production as it put the BOM up more than I wanted it to........maybe I'l re-visit it eventually.Ian.

author: The Soulman
author_rank: Super Contributor
timestamp: October 10, 2018, 08:44:16 pm
content: lm317 and one resistor? aprox. 30ct in small quantity's.Performance may vary but I have had good luck with mine, used in various projects/applications.About max 0,02% deviation over a couple years time, with cheap components.

author: Mechatrommer
author_rank: Super Contributor
timestamp: October 11, 2018, 12:42:10 am
content: 2 transistors and a resistor?

author: coppercone2
author_rank: Super Contributor
timestamp: October 11, 2018, 01:02:06 am
content: the ref200 is 25ppm/c

author: SiliconWizard
author_rank: Super Contributor
timestamp: October 11, 2018, 02:01:48 am
content: Another IC to consider is the TL431 which is much cheaper than the REF200. You can build constant current sources/sinks around those with just a couple resistors and a transistor. Overall cost < $1.I doubt you'll quite get the performance of a REF200 but it's cheap.

author: David Hess
author_rank: Super Contributor
timestamp: October 11, 2018, 03:54:41 am
content: The LM334 produces an adjustable precision current which is proportional to absolute temperature but can be temperature compensated with an external diode.The best way to build a precision floating current source is with an operational amplifier and precision reference. Check out the LM10 datasheet for an example; the same configuration is used for operational amplifier 4 to 20 milliamp transmitters.