First post in EEVBlog Forum.
Looked for an answer to this first but couldn't find it discussed yet - I hope!
TLDR: Why do some +/- rail PSUs have a lower current rating on the negative rail, and can I use switch-mode supplies for audio amplification.
I have come across this a few times before, and now that I am needing to buy an embedded switch-mode PSU it seems to have cropped up again.
When I am looking at the current ratings for the off-the-shelf triple-output PSUs I see something like : +5V/2A +15V/1.5A -15V/0.5A
So the negative rail current rating is much lower.
Is this related to the bias/supply for op-amps, or the fact that certain circuits need a bit of voltage in the negative? But that makes no sense, because it's not the voltage that is lower, it's the current..
I remember when I was doing a simple voltage inverter with an op-amp I think I needed at least some voltage on the negative rail for the amp to behave itself.
But I am wanting to amplify audio with this supply, so I want the same current capacity on both the rails don't I? In a Class A amp it takes equal amounts of current from both rails doesn't it?
Am I just looking at PSUs that have ratings for different applications than what I want, and I should just keep looking for a symmetrical-current supply?
Just so you know - the 5V is for digital stuff, and of course as I have said the +/- 15 for audio - op-amps and bi-polar transistors.
I could build my own linear supply (which I would prefer...), and have done so many times before, but space is getting to be a problem, so if one of these off-the-shelf switch-modes can give me the 3 voltages and currents I need then I will save space.
But this lower-current negative rail is kinda got me scratching my head and second-guessing myself.
And also I bit worried about using a switch-mode for audio - both the noise in rails and having a switching device in the project itself.
Has anyone had any experience with using a switch-mode for audio amplification, and is it OK or are there potential problems?
Any information about this would be of help - thanks!