TLE2426 Rail Splitter

[spongebob]

Has anyone ever used one of those?

Texas Instrument's TLE2426 The 'Rail Splitter' Precision Virtual Ground

These little things provide a stable low impedance virtual ground, output voltage = 1/2 input voltage. Could work very well as a replacement for those resistor dividers in battery-powered opamp circuits.

After reading the other thread about 'free samples', I ordered a few of these! :mrgreen:

[Tim Escobedo]

Looks like a good enough idea. Tell us how it works.

You can do the same thing with a unused op amd, or as R.G. pointed out recently, a LM386. However, this might be a better solution if the price is right.

[The Tone God]

Precession voltage reference componets are really intended for devices that need VERY accurate voltages for calibration like instrumentation. Its also intended to work off of constant supplies like adapters. The changing voltage of a battery through use will eventually make it go funny. Probably before the effect your using would die if you use normal voltage reference techniques.

Opamps in audio applications are fairly tolerant of their bias point more so then the level varience that you would get from standard parts. A high level of precession is not needed. They are not going to be any better then the old resistor devider plus cap. Your not saving much using one over a few discreet parts. If you design something using them you will have to chase down a weirdo part to make your effect work.

Just my opinion.

Andrew

[Paul Perry (Frostwave)]

For a buck and a half, I'd use it if I needed exactly 1/2 Vcc. (Mouser & Digikey). Note max output is 20ma.

[mike darling]

They work great. I've been using them for some time in my stompboxes, headphone amps, and other battery powered devices. They draw much less current then resistive dividers and my 9V's last MUCH longer.

Mike

[R.G.]

I proposed the more general use of the TI rail splitter chips quite a ways back, for the same reasons that they're up again now. They're neat, small, only three pins and do a great job of something almost every pedal needs.

Here's the problem I ran into - I could not find a distributor that kept them in stock for sale in small quantity. Mouser is out, and Digi-key, which normally keeps great stock of things outside Mouser's purview also does not carry them. At least they didn't when I last looked.

TI sent me samples, they're great, but with no easy way for people to actually get one, I gave up on recommending them.

Maybe they're more available now - that would be great.

You can do almost the same thing with an LM317  in the TO-92 package. You still need a couple of resistors to set the output voltage, but the idea is the same.  At least these are available, not made out of pure unobtainium.

[bobbletrox]

a) So 9v goes in and it spits out 4.5v?
b) What's the common for then?
c) What's the noise reduction pin on the 8-pin version for?

[mike darling]

a) So 9v goes in and it spits out 4.5v?
b) What's the common for then?
c) What's the noise reduction pin on the 8-pin version for?

a) it basically splits whatever voltage you put it across. so yes, you put it across 9v and you'll have 3 output terminals : 0v, 4.5v, 9v.

b) dunno what common you're referring to (i don't have the datasheet downloaded) Just use the 4.5v output as your signal ground and you have a bipolar supply to keep your opamps happy.

c) don't mess with the pdip. all you need is the T092 package.

[Tim Escobedo]

What about bypassing the virtual ground? Can you get away without some caps there?

[mike darling]

Yes you can use bypass caps with them. See this schematic:

http://www.tangentsoft.net/audio/ppa/amp/misc/schematic5.pdf

[mike darling]

Tangent used to have them for sale in small quantities on his parts page, but i didn't see them just now. The headphone amp people over at headwize love these - maybe smallbear could start stocking them  It would be good for us, and Steve could get some more customers if he really wanted to. They already love his pad-per-hole perfboard...

If one thinks ahead a little when laying out a PCB, it's not hard to allow for both the TLE splitter and a resistive divider - let the builder decide what is the best option for them. The T092 package is just so damn easy to use...

[Ed Rembold]

One word of warning-
If your design uses various levels of B+,
and you use rail splitters to provide 1/2 B+ for bias,
you're going to have trouble
with oscillations which will be very hard to find the cause of.

Bypass cap ESR also becomes very important,
using these things.


Ed R.

[Jason Stout]

RE: heads up, Thanks Ed.

[Paul Perry (Frostwave)]

Certainly, using a 'normal' op amp as a rail splitter often leads to tears (and oscillations) but, the TI railsplitter is optimised for one thig in life, viz generating 1/2 Vcc at low impedance. I don't think it is fair to compare it with say half a TL072!!

[MR COFFEE]

Ed and all,
The TI rail splitters are real stable, even with lots of capacitative loading to V+ or ground. Like Paul says, not like using a garden variety op amp.

I like them a lot, just haven't caught on as big as (I think) they should've.

FWIW,

[Jay Doyle]

I've only used them in one design, a Shaka-esque type clipper. I didn't have any problems and when I did a layout, it saved a ton of space on the board. Someone else uses the pedal, and hasn't reported any problems.