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Amplifier transistor matching?

Many of the current crop of flash MP3 players seem to use a single alkaline or NiMH AAA cell.

Chances are you're going to use a switching regulator anyway if you want good battery life. Otherwise you're probably throwing away more than half the energy.

It's a complex comparison-- case size, styling, and battery life and often charger considerations have to be taken into account in a portable product. I don't know how much the newest small stepup converters cost in consumer production volume, but mature SMPS chips are in the 10 to 20-cent range. The newest ones could be 5 or 10 times that, even in volume.

The size of things like digital cameras, games etc. have decreased to the point where they often insist on newer types of batteries. These things are expensive to replace, and you can't take advantage of improvements in technology. My first digital camera took 4 AA cells, and I now use 2450mAh batteries in it. The first ones were 1300mAh. That's a considerable improvement (over 6 years). My more recent purchases use special Li-ion batteries. At least one company is pushing security chips to prevent the use of third-party battery packs in new designs. Li-ion cells also need a more sophisticated charger technology AFAIUI.

But compare a typical Li-ion cell-

3.7V output. 5.5mm x 34mm x 50.4mm and only 21 grams. 860mAh at 3.7V. That's almost half the thickness of a AAA cell and has about the energy storage capacity and voltage output of 3 typical AAA cells. Very tempting.

Yes, I would think it would be good. Or even a AAA*. But the little flat Li-ion batteries would be even sleeker.

  • pronounced "triple-A", hence the "a".

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany
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No, *definitely* not. The last one I bought (Creative) has a blue LED display backlight. That requires 3.5V. ;-) Similarly with the Nike/Philips.

Which may not trouble the OEM so much. 8-(

Best regards, Spehro Pefhany

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Reply to
Spehro Pefhany

P.S.

I just looked, the Nike/Philips unit uses a Sigmatel 3410L SOC which has the DC-DC converter logic on chip (along with the 65MHz DSP, USB interface and lots of other stuff). It uses a (relatively) large external 4.7uH inductor and what appears to be quite a few other discrete (cheap) components. The only ICs are the SOC and two Toshiba TC58DVM92A1FT00 512Mb flash memory chips, the rest of the 150 or so parts are discretes, not even an IC audio amplifier.

(photos about 200K each on 0.2" quadrille paper)

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(the inductor is the large black square to the lower right of the SOC)

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Best regards, Spehro Pefhany

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"it\'s the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com
Reply to
Spehro Pefhany

In article , Spehro Pefhany wrote: [...]

If you are doing modest quality audio, you may not put the regulator in the circuit but instead use a class-D audio output.

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kensmith@rahul.net   forging knowledge
Reply to
Ken Smith

[....]

The numbers are in another part of this thread, kindly posted by someone else and they support my suggestion.

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kensmith@rahul.net   forging knowledge
Reply to
Ken Smith

So the casing of a AAA cell (and cell holder) doesn't do exactly the same? Not to mention all that wasted area between cylindrical cells.

I note you have included NO data to back up your assertion. Your claim of more energy per unit volume is looking dubious then.

MrT.

Reply to
Mr.T

Interesting to see some actual data for a change, however it would be more appropriate to compare batteries of the same range, and similar size. I am not familiar with the GP cells you refer to, but I suspect the top of the range AA cell is a newer technology. If you now use D cells instead, the figures are MUCH greater in favour of D cells than AA. Obviously by your reasoning nobody should ever use AA cells since D cells are far better!

In fact using only one D cell with a DC-DC inverter *IS* the best way to power most equipment! I'll let you do the calculations, then compare the cost of one D cell versus six AA cells!!!!!!!!!

Personally I would NEVER consider six AA cells as a good replacement for a

9V battery when a **FAR** better option exists.

And a D cell much further still. Now where are the figures for six AAA cells and battery holder?

Shame you cannot use that wasted space between cells.

As is the size difference unfortunately.

MrT.

Reply to
Mr.T

I used the alkaline Energizer Industrial series, because Digikey sells them. All capacities are to 0.8 V per cell, at 25 mA. That puts 9V batteries at a slight disadvantage, because that is more watts with a 9V than a 1.5V, but it looks like the error is small enough that I wouldn't do better trying to read a capacity off the graph.

The prices are in ones. They provide a volume, which appears to be more or less the volume of the cylinder, but I also calculated the `bounding box' volume.

AA cell: m=23 g, Q=2779 mA*h, E=4168 mW*h, $=0.75 CAD, V=8.1 or 9.8 cm^3 E/m = 181, E/V = 515 or 425, E/$ = 5557

D cell: m=142 g, Q=20500 mA*h, E=30750 mW*h, $=1.69 CAD, V=55.9 or 69.4 cm^3 E/m = 216, E/V = 550 or 443, E/$ = 18195

9V battery: m=45.6 g, Q=625 mA*h, E=5625 mW*h, $=2.86 CAD, V=21.1 cm^3 E/m = 123, E/V = 267, E/$ = 1966 6V lantern battery: m=665 g, Q=18000 mA*H, E=108000 mW*h, $=13.02 CAD, V=440.4 cm^3 E/m = 162, E/V = 245, E/$ = 8295

The energy figures are wrong because the voltage declines during the life of the cell, but they will be equally wrong for all types so I think that the numbers can be compared.

So that means that a AA cell is twice as good as (E/V) or 50% better than (E/m) a 9V battery. A D cell is about as good as (E/V) or 20% better than (E/m) a AA cell. That is sort of like what I expected.

What's wrong with the lantern battery though? Is there a good reason why it's worse or did I make a silly mistake somewhere? Different capacity vs. internal resistance tradeoff?

Jonathan

Reply to
Jonathan Westhues

In article , Mr.T wrote: [....]

I think the figures are no more misleading than many.

Pry apart a 9V battery and look at how the cell is constructed. There is very little there that is not the active part of the cell.

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kensmith@rahul.net   forging knowledge
Reply to
Ken Smith
[snip]
[snip]

Joerg, Which G2 model (lapel mike, with receiver) do you recommend? Thanks!

...Jim Thompson

-- | James E.Thompson, P.E. | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona Voice:(480)460-2350 | | | E-mail Address at Website Fax:(480)460-2142 | Brass Rat | |

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| 1962 | I love to cook with wine. Sometimes I even put it in the food.

Reply to
Jim Thompson

It's not ME bitching about them. I only use them when appropriate.

No.

Yes I read it, and still say a D cell has more energy per unit volume. Possibly per unit weight, but I'll let you do the calculation for that if you like :-)

a

Six alkaline cells = 9V, so I assume you are now talking NiMH. Of course that only makes the situation worse size wise anyway. However comparing apples with oranges does confuse the argument somewhat.

Yes, they are on the major battery manufacturers web sites.

Nor I.

I can't say I've seen any of those clever designs then.

If you weren't stuck in the same groove, you might realise putting something THREE times the size into a device which is supposed to be SMALL, is not necessarily an option. In this instance I am talking about SIZE period, not volumetric efficiency.

Run it off a Car battery if size is NOT an issue!

MrT.

Reply to
Mr.T

the

for

The figures are rather misleading, but you are probably correct this time. Your "I suspect that the cells in the 9V are actually a little better than the AA in energy per volume" is still doubtful though. I still think a DC-DC inverter is the best solution, as you can have small and/or higher capacity as well as lower battery costs. However this thread is getting too far into comparing apples with oranges, IMO.

MrT.

Reply to
Mr.T

You may wish to check the From: header. That was my first post to the thread.

Jonathan

Reply to
Jonathan Westhues

if

Thanks for showing that I was right and a D cell does in fact have more energy per unit volume, and is FAR better in energy per dollar. Frankly I couldn't be bothered going to the trouble you have, so I'm impressed you did even though it proves you were wrong.

Which puzzles me why you claimed otherwise then?

They have always been a rip off such that adapters were even made to fit 4 D cells instead. The E/V is pretty similar to the other rip off, the 9V battery though.

MrT.

Reply to
Mr.T

Hello Rich,

Yes, but that would be a kludge. It isn't rocket science to design stuff so it can work off a couple AA NiMH. What's the big deal?

Regards, Joerg

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Reply to
Joerg

Hello Arny,

You can build your own DC-DC with cheap logic chips and that works just fine down to 2V.

Also, nearly any function can be achieved with circuitry that works at

2V without a converter. I am glad that Sennheiser has finally done it as well. Their G2 mics can take two AA NiMH. Way to go. Thing is, if they hadn't done it we wouldn't have bought their stuff anymore.

Nah, the last one I designed was well under a Dollar. Ok, mass quantities but even with low qties it wouldn't have been a lot more.

Yes. But it requires that engineers learn to design down to transistor level again. With opamps it usually isn't going to work without the cost going through the roof.

Regards, Joerg

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Reply to
Joerg

Hello Jim,

Don't know yet but I will have to figure that out anyway for our church. Probably this weekend. When I found out I'll let you know. First I'll have to find a reasonable dealer (good prices) but that's the easy part.

Regards, Joerg

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Reply to
Joerg

My sincere apologies.

MrT.

Reply to
Mr.T

By the way, while many op-amp circuits published specify a supply coltage of

+- 15 volts, or +- 9 volts, many circuit designs will work with +- 3 volts, which is easily achieved with two pairs of AA cells.

Also, many circuits will take more power from one side of the power supply than the other; so if you're using batteries to provide a +- power supply, it's worth testing them to see if only half need replacing.

Tim

Reply to
Tim Martin

transistor

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I just had to bash the hell out of a mini Maglite to get the innermost AA cell out of it. It had started to leak and the corrosion on the end was just enough to prevent it from coming out. I had to smakc it against a concrete floor, with a few layers of paper towel on it to give just a small amount of give.

Reason for saying this is that it'e really poor advice to give to reuse half spent batteries. Works really great if the equipment takes a single cell. But if you put a half spent battery in series with a new one, it's likely that the half spent one will be discharged to zero and beyond, leaking in the process. I think if I had two of four cells run down faster than the other two, I would swap the sets halfway thru their life. Better yet, get a piece of equipment that's not so poorly designed that it runs down one set faster than the other.

Reply to
Watson A.Name - "Watt Sun, th

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