We have a conundrum. Any device that truly amplifies (increases) POWER, watts rms, could rightly be called a power amplifier, regardless of intent or scale. Does the output power exceed the input power? Yes?, well then it's a power amp, by definition.

But that may not be a useful definition and we feel uncomfortable applying the term when the scale is too small (as MrChips just noted) or (as stuidot noted) when the intent is something other than driving a transducer to convert electrical energy into heat or motion.

So the conundrum is that not everything that amplifies power is commonly called a power amplifier.

I don't know what the heck a voltage amplifier is and is not. Everything with a voltage gain >1 is technically amplifying the voltage, but my transformer example was rejected. And I'd reject a voltage divider as being a "voltage amplifier" with gain <1.

 

If we really want to be nitpicking LA4537MC is a stereo headphone power amplifier that can deliver 8mW into 16Ω headphones. That's like 24mA output.

 

If we really want to be nitpicking LA4537MC is a stereo headphone power amplifier that can deliver 8mW into 16Ω headphones. That's like 24mA output.

I would argue if the input signal can't deliver that current on its own, it's a power amplifier. Otherwise, if a device increases current without appreciable voltage gain, we have to define what this third kind of amplifier is, that isn't a voltage amp and isn't a power amp.

Re: the other ongoing point of contention, I don't think calling a stage that decreases voltage an "amplifier" is appropriate. Active attenuators are a thing!

 

I don't think calling a stage that decreases voltage an "amplifier" is appropriate. Active attenuators are a thing!

If an amplifier outputs less amplitude than the input, then it is considered to have a gain less than one.

 

If an amplifier outputs less amplitude than the input, then it is considered to have a gain less than one.

Definitely...but here we're coming to a semantic crossroads that again involves intention. If I turn down the volume on a Marshall stack, it's still an amplifier, even if the gain goes <1...the device is intended to amplify. But if I deliberately build an inverting op-amp stage with a feedback resistor bigger than the input resistor, I would argue that stage isn't an amplifier, it's an attenuator.

 

I agree that this thread is mostly a semantics discussion. I also see a lot of miss labeling between what something is and what it does. A amplifier is still an amplifier even if it attenuates. A transformer is still a transformer even if it gives you a voltage gain.

 

I also see a lot of miss labeling between what something is and what it does.

Wait...is that a buoy? I think this is officially the deep end...

 

OH buoy!! think so?

 

OH buoy!! think so?

I mean, I don't want to make waves...

(Also, it would help my rhetorical points if I could get my facts straight...I meant a feedback resistor SMALLER than the input resistor, of course...)