[Navyblue]

I'd like to build a portable amplifier using 4x1.2V rechargeable AA. However 4.8 V is kind of low for supply voltage.

Please recommend me some sort of IC (or even discrete solution) that I can double or even quadruple my supply voltage yet small enough to fit into a mint tin? Or if possible I want to use 2xAA (2.4V) and multiply it by 10x.

Thanks.

 

[JamesL]

I'm not very experienced, so I'm not going to try attempt the question, but wouldn't it be easier to use a rechargeable 9v battery?
They're basically made of 6 x 1.5v cells in series, and would also fit in a mint can.
You can't draw energy out of thin air, so you'd need to lower resistance or current somehow, and somehow, I don't think thats a good idea.

 

[Navyblue]

I am not drawing energy out if thin air, I use batteries.

Voltage doubling is a common thing in electronic.

 

[JamesL]

Lol right... like i said, don't listen to me.
I'm pretty much only self-taught in electronics, so I'm not one to be saying anything. =x

 

[Navyblue]

No problem

, I'm trying to self learn too, thanks to helpful community like this.

I think quite a few commercial amp does voltage doubling somewhere, especially those that uses lithium batteries (not very high voltage), but probably not in a way that I'm planning to do.

 

[Hardcoreckn]

You might want to look into something called a "Boost Converter" / "DC to DC Converter" / "Step Up Converter". You'll most likely find stuff that can do 2x. 4x is pushing the bill.

 

[Navyblue]

I've seen a rather simple circuit using opamp to amplify the voltage. However I don't know enough to know how the circuit should look like and which opamp to use.

However, I found this:

XP POWER | IE0524S-H | Power Supplies & Converters | Electrical & Circuit Protection | Farnell SG

It looks like it would convert 5V to 24V. 4xAA is 4.8V I guess that's close enough. But how do I use this?

 

[adamus]

how much current will you pull? too much and the batterys wont have the discharge rate to keep up with 24v.

 

[Navyblue]

I don't know, it's most likely for a CMoy. I guess not a lot? Or depends on headphone being used?

 

[00940]

Maxim has tons of boost converters. See the table here : Maxim - Parametric Search - Product Table

At first sight, the MAX1790 seems to be what you're looking for. It will give 12V regulated with 3 or 4 AA batteries. It's switching at high frequency which is good in your application (the faster the better I'd say). For higher voltages, there's also the MAX1522. Of course, all that stuff comes in smd packages.

 

[error401]

Most DC-DC converters are a bit of a pain for DIYers, which is why you don't see them too often around here (I presume).

That said, they're not that hard to apply if you read the datasheets carefully. National even has a web app that will help you design your power supply with their chips, including selecting external components for you. Pretty handy if you don't know how to choose the correct inductors and such.

The easiest solution I've seen is probably the TI DCP02 series - they come in DIP package, have versions that produce both +/-15 (or 12)V from a 5V source, and only require a couple caps for external components. They're a bit expensive, but it doesn't get any easier.

One thing to watch out for with any DC-DC converter is switching noise, which can often be quite bad. You may need to apply a strong low pass filter on the supply, or use a post regulator that rejects high frequency noise (ie. not the 78xx or 317). If your amp has good PSRR you might not need it.

 

[Navyblue]

Thanks guys for your inputs.

Maxim offer some "low noise" models, not sure if they were actually any better.

So how do I apply those? I guess can't just connect them like I do with batteries? Would simply connecting a capacitor in series does it?