If a tle2426 only handles 20-40ma, can i limit batteries current with a resistor?
Apr 1, 2006 at 10:53 PM Thread Starter

#### joostoo

Hey, im making my own cmoy layout, and i need help with the grounding a bit. im using a tle2426, but according to tangents site, it can only handle 20-40mah of current. the 9v battery im using gives out 150mah, so can place a resistor before the tle2426 to limit the current down? Or should i just leave it as is?

thnx

Apr 1, 2006 at 11:29 PM

#### Clutz

##### Tells us when we're offset.
You're confusing the units: The TLE2426 can only handle 20 to 40mA (milli Amps) of current, and a 9V battery has 150mAh (milli Amp hours). This means that the 9V battery can produce 1 milliamp of current, at 9 volts for 150 hours, or 2 milliamps of current at 9 volts, for 75 hours, etc. etc. What tangent means when he says that the TLE2426 can only handle 20 to 40mA of current, is that it can only support a 20 to 40mA of current DRAW from it.

Hope this helps.

Apr 1, 2006 at 11:39 PM

#### cetoole

The 150mAH is not the current the battery puts out, but rather the amount of current the battery can provide, in mA, for one hour (mAH=milliamp/hour). You do not want or need to limit this, larger mAH rating just means your battery life will be longer. Current is not like voltage, in that it is drawn as needed by the amp. 20-40 mA is just the amount of current the TLE is able to draw

Wow, beat by clutz, my internet connection is goind really slow today.

Apr 2, 2006 at 12:42 AM

#### vixr

So, does this also mean that if you had a high current design, like a buffered class A amp using a 2132 chip, 5484s and 5486s and two buf634s, the 2426 would not be able to supply enough current? My latest amp is using all this stuff and doesn't go crazy loud like an amp powered by a divider resistor power supply... Maybe a single output op amp like a opa134 would be a good rail splitter... Sorry about the thread hijack joostoo, it looked like a good fishin spot. Well, a quick test proved it... My amp is drawing 130mA at max volume... Time to regroup...

Apr 2, 2006 at 1:12 AM

#### cetoole

Quote:

 Originally Posted by vixr So, does this also mean that if you had a high current design, like a buffered class A amp using a 2132 chip, 5484s and 5486s and two buf634s, the 2426 would not be able to supply enough current? My latest amp is using all this stuff and doesn't go crazy loud like an amp powered by a divider resistor power supply... Maybe a single output op amp like a opa134 would be a good rail splitter... Sorry about the thread hijack joostoo, it looked like a good fishin spot. Well, a quick test proved it... My amp is drawing 130mA at max volume... Time to regroup...

Looks like the 134 cant put out much more than a 2426, what you need is a buffered rail splitter. Check out http://www.tangentsoft.net/elec/vgrounds.html

Apr 2, 2006 at 3:52 AM

#### vixr

Wow, thanks for the link... That buffered design is perfect. Tangent is pretty amazing.

Apr 2, 2006 at 3:58 AM

#### thedoctor

Quote:

 Originally Posted by vixr So, does this also mean that if you had a high current design, like a buffered class A amp using a 2132 chip, 5484s and 5486s and two buf634s, the 2426 would not be able to supply enough current? My latest amp is using all this stuff and doesn't go crazy loud like an amp powered by a divider resistor power supply... Maybe a single output op amp like a opa134 would be a good rail splitter... Sorry about the thread hijack joostoo, it looked like a good fishin spot. Well, a quick test proved it... My amp is drawing 130mA at max volume... Time to regroup...

two buf634 as in one for each channel? as in unbuffered ground design? maybe you should try buffering the ground channel with a BUF634 or with an Opamp (like the OPA134 that you've mentioned up there).

the OPA134 isn't used as a rail splitter, but as a buffer to buffer current draw from the virtual ground. you could use a discreet diamond buffer (which i think is better than an Opamp in there but at the cost of complexity), an Opamp working in unity gain, a BUF634 or any other buffer chips, or you could make a ground channel from the same schematics as the left/right channel (with no gain).
i've posted a pic from sijosae's about vground designs a while back.

Apr 2, 2006 at 4:23 AM

#### joostoo

Oh, ok thnx so much. Its funny how something so simple such as units could cause so much confusion So basically the 2426 will only take as much current as it needs?

EDIT: so my 150 mah battery will only last approx 3.75 hours (150mah / 40ma)??

Apr 2, 2006 at 5:08 AM

#### ericj

A load on any circuit will only take as much current as it needs.

The tle2426 itself needs very little current - what we're talking about here is it's ability to sink current to the rails to maintain the virtual ground potential.

When you're done building your amp, you can measure the current draw when it's playing into headphones and guesstimate how long the battery will last. It's probably much less than 40ma.

Apr 2, 2006 at 5:36 AM

#### vixr

So thedoctor, when a unbuffered ground channel is used in a buffered left/right design it actually uses more current? I understand how the 2426 could be used to create Vgnd and the 134/buf would create the Ognd, but this wouldn't raise the overall current draw even higher than what I have now? (appx. 130 mA)

Apr 2, 2006 at 7:38 AM

#### cetoole

Quote:

 Originally Posted by vixr So thedoctor, when a unbuffered ground channel is used in a buffered left/right design it actually uses more current? I understand how the 2426 could be used to create Vgnd and the 134/buf would create the Ognd, but this wouldn't raise the overall current draw even higher than what I have now? (appx. 130 mA)

Yes, you are adding a third channel of amplification to the current draw, this is probably the largest downside to this approach. For portable amplification, it gets to the point where one must ask themselves if a true dual rail PS wouldnt make more sense.

Apr 2, 2006 at 7:44 AM

#### thedoctor

Quote:

 Originally Posted by vixr So thedoctor, when a unbuffered ground channel is used in a buffered left/right design it actually uses more current? I understand how the 2426 could be used to create Vgnd and the 134/buf would create the Ognd, but this wouldn't raise the overall current draw even higher than what I have now? (appx. 130 mA)

current are needed by the buffers to operate. if you add a TLE24246 and another OPA134 to the ground channel for both the VGND and OGND, then yes it will raise the current draw of your amp than your current one. and are you sure it sucks 130mA in current config? that's a very high number for 2 channels even with buffers.

Apr 2, 2006 at 1:09 PM

#### Garbz

careful with the figures. The extra current draw is not as much as say going from one channel to 2. The extra channel actually sinks current in a way from the active channels. The extra current draw is likely to be in the very low mA range prehapse less.

Apr 2, 2006 at 5:56 PM

#### vixr

Thanks guys... I have a nice breadboard, maybe I should lay this all out there and not be so qiuck to fire up the iron... The funny thing is, I have all the documents printed out in a binder, everything is spelled out. I just didn't read it.

Apr 4, 2006 at 9:27 AM