Simple voltage reference using jellybean parts? - Page 1
Forum section: electronics / beginners

author: MoighonFweeman
author_rank: Contributor
timestamp: March 19, 2015, 12:39:11 am
content: I need a very simple 1V reference with only jellybean parts. The two most important things are that it draws very little current, and that the output reference does not depend on the input voltage, which may vary from 6 to 15 volts. In fact, it doesn't even have to be 1V. Any low voltage will work. I can regulate it down with a resistor divider, because I'm not driving any kind of load.I've considered a zener shunt reference, and simply regulating the output of a 7805 down. However, the zener reference draws too much current, and I'd rather use a more elegant solution than a 7805 if possible. Any ideas? Thanks.

author: dannyf
author_rank: Super Contributor
timestamp: March 19, 2015, 12:43:07 am
content: TA78DL05 - a bitch to use but does the job.There are tons of other low-idle current regulators as well.

author: Marco
author_rank: Super Contributor
timestamp: March 19, 2015, 01:19:49 am
content: X431 Shunt regulator with large series resistor?If the stability of a standard linear regulator is good enough I don't see what's inelegant about using it though.

author: MoighonFweeman
author_rank: Contributor
timestamp: March 19, 2015, 01:23:57 am
content: I don't want to actually buy a voltage reference part. That's what I meant by "jellybean parts".Quote from: Marco on March 19, 2015, 01:19:49 amThis voltage reference is going to be used as part of a power supply unit. I already have a LM317 in the unit, so I really don't want a separate regulator just for this. I guess a LM7805 would work though. It also solves the problem of how to drive a "ON" indicator light at constant current. Hmm.

author: Marco
author_rank: Super Contributor
timestamp: March 19, 2015, 01:44:50 am
content: The Vadj input on your LM317 is approximately at 1.25V, can't you just use that?

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: March 19, 2015, 03:12:14 am
content: 0.5mA LED?http://www.digikey.ca/product-detail/en/HLMP-P156-EG031/516-3056-1-ND/4240302Plus it glows!

author: cellularmitosis
author_rank: Unknown
timestamp: March 19, 2015, 07:51:22 am
content: Could you use the famous two transistor current source? The reference could be a resistor which you drive the current through.That's two 2n3904sand three resistors. Hard to get much more jellybean than that.

author: mij59
author_rank: Frequent Contributor
timestamp: March 19, 2015, 07:55:20 am
content: Something like MCP1700, ZXCL330, LP2950, LM385, HT7130 should work.

author: rdl
author_rank: Super Contributor
timestamp: March 19, 2015, 04:04:30 pm
content: I keep a similar circuit built on my larger breadboards to serve as a kind of pilot light. Two 2n2222 transistors, a couple of resistors and an LED. Keeps the LED current between 7 and 9 mA from 5 to 16 volts and only uses 5 column x 4 row area on the breadboard.Quote from: cellularmitosis on March 19, 2015, 07:51:22 am

author: JohnnyBerg
author_rank: Frequent Contributor
timestamp: March 19, 2015, 04:26:46 pm
content: LM385 + 1 resistor.LM385 can work with 10µA and is very cheap.Output voltage is 1.235VMy new low cost reference that is coming soon can use a LM385 or a LT1004