power amplifier

[TeamTEOR]

I am looking at makeing some type of lightweight power amplifier
circuit. I need to take 3v @1.2a and bring it up to 8-9v and about
3.5amps.

I spoke to the people over at digikey, and they suggested to start with a 2N5192OS-ND transistor. Can anyone help out a little more on this?

[Andy W]

You can't increase voltage AND current.
Power is power. (3Vx1.2A=)3.6W in cannot mean (8Vx3.5A=)28W out..

A 3V source required to produce 3.5A @ 8V requires 28W, which means more than 9A @ 3V..
..a

[Dan Baldwin]

What is it you're trying to do?

Dan

[Norman Adlam]

You can't increase voltage AND current.
Power is power. (3Vx1.2A=)3.6W in cannot mean (8Vx3.5A=)28W out..

A 3V source required to produce 3.5A @ 8V requires 28W, which means more than 9A @ 3V..
..a

Or more like 12A-ish, with losses! :(

Cheers

[Andy W]

Indeed.. my example assumes 100% efficiency..

[zagisrule!]

You need a small SMPS for this application, I am unsure about using other types of boost converters at currents that high.



-Matt

[C Andrew Green]

Hi TT,
I think when you spoke to DigiKeys people and said "power amplifier" they thought 'Audio power amplifier' or something like that. What I think you mean is a DC-DC converter, I deal with them every day and what Andy W says is true and also as Norman says you need to allow for the losses, we work on a typical conversion efficiency of 80%. If you want some idea of what's available try http://www.xpplc.com (XP Plc (UK but with USA availability), If you look http://www.xpplc.com/orderPriceList.taf?seriesid=100134&groupid=100033&catuid=2# (here they list a 3V I/P that can supply 111mA at 9V (and many others) but remember to allow for 20% losses.

Regards

Andrew

[KnimRod]

No matter what (Watt), you can't convert 3.6 Watts to 28 Watts (effectively more than 700% efficiency) which are what TeamTEOR's parameters state. If anyone does figure out a way to do it, they best get a patent because it will certainly make them rich. :)

[TeamTEOR]

Wow, I was hoping that I could find a couple of light transformers & a voltage regulator that might bring up the voltage to allow for it to be lowered back down with some extra amps.

What I was hoping to achieve was a R/C solar powered car. Being that I live in Scottsdale, AZ I thought it would be cool to put that sunshine to some good use. If I was able to keep it really light maybe I was able to try going to try a plane of some type using carbon fiber rods and lightweight fabric or maybe a boat made from Bluecor.

Not for nothing, they have pool fountains ran by solar cells that can shoot water 3-4 feet up in the air... They should be able to power some small motors for projects like these.

I found some solar panels with these specs:
2-Q LAMINATE
* thin-film amorphous silicon, 216mm x 105mm (1mm thick)
* output 300mA at 3V (stable)
* flexible, virtually unbreakable
* light-weight (50g with pinch terminals)
* waterproof, high power/weight ratio
* durable, 20year useful life
* responds to diffuse light [light scattered by cloud cover]
* pinch terminal connections allows for easy connection to devices

[Terry S]

use enough solar cells to give you more than your required voltage so that you can charge a battery then work on a very efficient motor/transmission system. any voltage convertors will just wast power.

Terry