Negative voltage generator - Page 1
Forum section: electronics / projects

author: Thane of Cawdor
author_rank: Regular Contributor
timestamp: March 15, 2014, 09:47:06 am
content: Hi,I've been searching for a way to generate smooth negative voltage for my op amp circuit so I can run it off a single supply. What is the simplest way to do this?P.S. I've already tried 555 circuits and I don't really want to buy specialised inverter IC's for this project.Thanks

author: Rerouter
author_rank: Super Contributor
timestamp: March 15, 2014, 09:50:46 am
content: if your playing with a 555 just rectify the output of the crude inverter and throw it through a linear negative regulator, (7905?)

author: Thane of Cawdor
author_rank: Regular Contributor
timestamp: March 15, 2014, 09:55:21 am
content: QuoteOk, will try to build it now

author: uwezi
author_rank: Unknown
timestamp: March 15, 2014, 11:38:16 am
content: Quote from: Thane of Cawdor on March 15, 2014, 09:47:06 amStill I would suggest you look into the MC34063. It probably needs fewer external components than any 555 circuit, is very cheap and easy to use. Just enter your values on thiswebcalculator. The schematic diagram on the page will automatically adjust to up-converter/down-converter/negative-output. See the screenshot below as an example.But be carefulwhen using this chip for the first time! For some weird reason it is the only chip I know where everyone uses the pinout as seen frombelow!

author: Thane of Cawdor
author_rank: Regular Contributor
timestamp: March 15, 2014, 01:02:39 pm
content: Hi,Couldn't I just use a simple MAX232's positive and negative voltage generator?Thanks

author: fcb
author_rank: Super Contributor
timestamp: March 15, 2014, 01:14:59 pm
content: I've used the ICL7660A in a few audio designs - painless and if you've got enough capacitance on the -ve rail - very low noise.

author: Thane of Cawdor
author_rank: Regular Contributor
timestamp: March 15, 2014, 01:21:09 pm
content: QuoteWould you know how much current it could supply?Thanks

author: BravoV
author_rank: Super Contributor
timestamp: March 15, 2014, 01:51:08 pm
content: Alternative cheaper non IC method using only discrete components, read it carefully here on the circuit design starting the one posted by Jay_Diddy_B and also few variants below it ->Starting from this post and go forward.Hope this helps.

author: Bored@Work
author_rank: Super Contributor
timestamp: March 15, 2014, 03:42:47 pm
content: eBay auction: #141047197560$1.41eBay auction: #380755874794$1.44Can easily be wired up to generate a negative voltage.

author: I_may_be_drunk_right_now
author_rank: Contributor
timestamp: March 15, 2014, 04:24:28 pm
content: Quote from: Thane of Cawdor on March 15, 2014, 09:47:06 amYou can't get away with biasing at 1/2Vcc? Is this a DC application? What is this "circuit"? Is it a secret? Tell us so we can give better answers, otherwise it's just pissing in the wind when after 235 replies you finally tell us what you really want.

author: TerminalJack505
author_rank: Super Contributor
timestamp: March 15, 2014, 04:48:19 pm
content: Did you try something like the attached with the 555?It should work fine so long as you don't need a lot of current or a regulated voltage.

author: johnwill
author_rank: Contributor
timestamp: March 15, 2014, 07:12:53 pm
content: basically there are two ways to generate negatives volatges from a positive source . A switching power supply with transformer or coil ..depending on your power requirements .. it can be as easy as a transistor and a coil. The second possibility is a "CHARGE PUMP " is basically an analog switch commuting the poles of a capacitor .. poe A is connected to positive source .. pole B is grounded .. is charged in time T depending of the cap capacity . Next cycle capacitor is completly disconnected from source and pole A is grounded pole B is connected to LOAD .. The best configuration is to have two caps while one gets charged by the source the other powers the load.

author: kg4arn
author_rank: Unknown
timestamp: March 16, 2014, 02:03:17 am
content: If you don't need too much current...