[enemigo]

I have been thinking about making a portable amp that runs from a single 1.5v AA battery. I thought about adding an amp configured to a gain of 5, giving 5*1.5v = 7.5v. What are a normal AA battery, a little below 1000mAh at best? Divide it by 5 for the gain and remove 40-50% for amp efficiency, and the battery should provide just below 100mAh at 7.5v. A normal 9v (E-cell) provide a bit above 100mAh, so the batterylife will be ok!?!

Problem is, this is not how it works, is it? I mean, otherwise I would think it far more common. So what are the problems? A severe degradation of the power quality? Any other problems? Any point in taking this idea further?

Edit: On second thought, I might be needing an instrument amp for a single side psu?

Thanks
Knut

 

[Porksoda]

Unfortunately, it's not that easy. Op-amps can at most drive their output to the voltage they are being powered with. So the op-amp would not be able to put out more than the 1.5 volts you give it.

However, there is a device that does exactly what you are describing, a DC-DC converter. Check out COSEL , they make an awesome selection of DC-DC converters along the lines of what you are looking for.

 

[Alick]

Sorry, this is not how it works. The op-amp will only be able to provide the configured gain up to (almost) the limit of it's supply voltage which is in your case ... 1.5V (unless I'm reading your post completely wrongly and I'm missing something daft).

 

[enemigo]

Ok, thanks... Had really hoped a voltage amplifier just multiplied the gain with the voltage potential between the inputs.

Edit: But the immense input impedance probably prohibits this?

Adding a DC/DC converter is probably the best solution, but that kind of defies the idea of saving space/weight, not to mention money

Knut

 

[00940]

check the usb dac project on the webpage of Guzzler. You'll see that dc-dc converters don't take much space.