Current source with two different output? - Page 1
Forum section: electronics / beginners

author: FriedMule
author_rank: Frequent Contributor
timestamp: November 16, 2022, 07:51:31 pm
content: Is it possible to make a current source that have two outputs of different current value?To save space and components, is it possible to build a precise current source that can output two different currents, one value on output one and another on output two?

author: magic
author_rank: Super Contributor
timestamp: November 16, 2022, 08:04:17 pm
content: Define "different", define "precise" and define "two outputs".Does it count if it's two pullup resistors of different values to 5V?Does it count if it's a dual opamp regulating two MOSFET current sources independently?

author: Benta
author_rank: Super Contributor
timestamp: November 16, 2022, 08:27:27 pm
content: And define current levels. 1 uA? 300 A? Voltage compliance?

author: FriedMule
author_rank: Frequent Contributor
timestamp: November 16, 2022, 08:58:31 pm
content: Oh I am so sorry!I hope to get two current sources with these specifications or better 5V 100mA (+/- 20uA) and 5V 35mA (+/- 2mA)But instead of having to make two complete current sources and place them side by side, am I hoping to make one current source but with two outputs, one with 35mA and one with 100ma.

author: bdunham7
author_rank: Super Contributor
timestamp: November 16, 2022, 09:16:48 pm
content: Quote from: FriedMule on November 16, 2022, 08:58:31 pmSeems simple enough as long as they don't need to be isolated. You can use the same +5V power source for each, but each output would need it's own current regulator. So a regulated 5V supply (like a transformer, bridge, capacitor and LM7805) followed by two LT3092 circuits (or whatever you choose). The only components duplicated are the LT3092 and two resistors.

author: Benta
author_rank: Super Contributor
timestamp: November 16, 2022, 09:22:57 pm
content: 100 mA +/- 20 uA?Do you have access to 0.02% sense resistors?Sounds like saving on the active parts is the wrong place to start.

author: FriedMule
author_rank: Frequent Contributor
timestamp: November 16, 2022, 11:01:23 pm
content: Yes it would be best to be able to build a complete PSU with everything but the space inside that old oven is not that big and the space inside the laser unit is isolated and is also limited in space... it just about fits.

author: FriedMule
author_rank: Frequent Contributor
timestamp: November 16, 2022, 11:02:50 pm
content: I thank you, it sounds as a great idea, do you maybe already have some drawing you may have used?

author: David Hess
author_rank: Super Contributor
timestamp: November 17, 2022, 03:29:26 am
content: A current source with two outputs usually means that they share the same reference, which is easy enough.

author: MrAl
author_rank: Super Contributor
timestamp: November 17, 2022, 05:32:02 am
content: Quote from: FriedMule on November 16, 2022, 07:51:31 pmWhy not? If you can build one you can build two.You would normally need separate feedback for both though unless you can assume that the current in each leg will be close to it's nominal design value. You of course need two separate outputs unless again you can assume the current in each leg will be close to the nominal value for each leg under all external conditions.