@BrianDrummond I have nothing to keep it cool... Just an op-amp sticking out of a bread-board. How could that effect output voltage?

@BrianDrummond Gonna take a big old heatsink and drop it onto the back of the IC. Let you know how it works out.

yikes... way over supplied.. use +-5V...

What is the cold resistance of that lamp?

Tried the +/-5V suggestion and the output generated voltage was only 1.2VAC, not the desired 5VAC. Also, adding a large heatsink did not help things at all. With the large heatsink, still had the RMS voltage dropped down to 3.6VAC which was a little bit better only... Let me get the cold resistance value on that lamp for you @Trevor_G

@Trevor_G 0.7 Ohms, including voltage probes attached... Is that what you wanted?

We don't have a datasheet for the lamp @Trevor_G It's OEM from another company. It's also very very very old, data for it does not exist.

@Trevor_G Also just noticed, I experienced some serious clipping when I dropped the supplies down to +/-5V... How would I reduce the clipping? Maybe that would end up fixing my problem after I reduce the clipping.

@SpehroPefhany I wouldn't go by that resistance measurement. There is a supply that we have which can handle the lamp properly... It draws 1A (rms) @ 5VAC. (not disagreeing with you) but I just don't understand where you get 10A peak exactly.

@SpehroPefhany Additionally, not much of an experienced power supply design person... I'll admit, I don't know what a bridging amplifier is. Will that help me with my problem?

@SpehroPefhany Okay... Just wanted to let you know that I don't think that 0.7Ohm measurement is worth all that much... Sorry I don't have much more on the characteristics of the lamp... That would really help this whole situation.

Te point is when cold incandescents are basically a short, the opamp will go into current limit before the lamp heats up to the operating current. Whether that is enough to get the lamp up to temp is unknown

@SpehroPefhany Okay, I see where you're coming from then. Thanks. Should I consider looking into how bridging amplifiers work then?

@SpehroPefhany a decent high current voltage follower stage after a cheapo op-amp would be enough... it's not like he needs hi-fidelity.

@Trevor_G Correct, the output waveform is pretty good and accurate right now... Just gets sucked down a little due to improper design.

@Trevor_G Is "follower stage" also called, "follower amplifier"? Just trying to figure out what to research. Trying to figure out the correct terminology as well.

Check out This cross-post

@SpehroPefhany yup that would be way more efficient, but likely a few floors above his head.

@Finbarr I was wondering that too.

@Finbarr 400Hz AC is a requirement for aircraft components. Sorry, for this aircraft component.

@Trevor_G The whole thing is a few floors above my head at this point. Stuck with someone else project, trying my best to come up with something in the wake of approaching deadlines...

Well good luck then, this circuit isn't it though, not unless you need a space heater too ;)

@Trevor_G When you say "this circuit isn't it though", I am just a little confused. Do you mean that I shouldn't be using a non-inverting configuration? Or, that I need to add a voltage follower in order to maintain the output voltage?

@Trevor_G Should I be looking into some sort of multi-stage amplifier configurations? I am not sure where to begin, sounds like it might work for me. Will keep reading about that for now unless I receive some other suggestions.

@Snoopy with 1.15A rms your amp is going to dissipate over ~50W... That's a low of heat to get rid of.

@Trevor_G Got the big heat-sink on there as suggested. Did you see the comment about the multi-stage amplifiers? Might that help things a bit? By the way I did read that answer you gave to another user about how the BJT solutions wouldn't quite work. I had some difficulty understanding your answer. Sorry if it seemed like I didn't respond or pay attention to that.

Multi stage wont help you, the final driver stage does all the work.

Hi Trevor, thank you for joining the chat.

Let me see...

So your thinking is that the input frequency of 400Hz has something to do with the problem?

Is there a little test I can do? Maybe like... increase the frequency or something and then see if the load doesn't get pulled down?

voltage doesn't get sucked down

No the frequency is fine, but the op-am at 48V rail delta will be horrendously inneficient... only about 10%... for the 5W the lamp takes the amp has to dissipate 10x that much.

Hmm... so the fact that it's dissipating that much is whats sucking down the voltage?

It may be overheating, but it is likely also because the start current is way too high.

How much voltage is being dropped over that 0.1R resistor?

Hmm... I've attached a large chunk of alluminum to the back to act as a heatsink...

One sec.

When I remove the heatsink, the output voltage sinks considerably... However when I re-attach the heatsink, the voltage droops only to 3.6V (which I realize is still way too low).

But without the heatsink it's like less than 3V...

Let me get that voltage drop for you.

(with heatsink attached)

The voltage drop across the 0.1 Ohm resistor is 92mV rms.

Hello Clabbachio, thank you for joining the chat.

ARe you looking at this on a scope or with a meter

True RMS Fluke 233 meter sitting right next to me! Should I be using a scope?

The rest of a discussion can be found at: chat.stackexchange.com/rooms/72724/…

Thanks @clabacchio

No problem!

It may be oscillating, using a scope will tell you.

Okay, let me check that out and I will get right back to you.

@Trevor_G I tried to measure directly across the resistor with a scope and the screens on all my power supplies turn off!!!

I double-checked, I am not even shorting anything!

I would not attach a scope across the resistor. find a decent gound and measure the output after the resistor

Okay, so you just want the output at the resistor? It's 3.6V rms.

Or you want before the resistor too?

is it a clean sine wave like you expect though...

Before the resistor = 3.64V rms

After the resistor = 3.57V rms

The sine wave is absolutely perfect!

Hi Finbarr, thank you for joining us!

what are the rails doing on the scope

Well, they seem to be a little bit noisy... But when I turned on the circuit just now I noticed that my -24V rail had 40V reading on the supply... When I disconnected the -24V supply from the circuit, the power supply was displaying 24V as it should be...

hmm ..something is off with your wiring

@Trevor_G Really? Just to verify... I did remove the lamp from the circuit and test the output voltage... When the lamp is removed the two rail power supplies read +/-24V respectively and the output voltage is 4.998VAC rms @400Hz.

So everything looks fine until I add the lamp back into the circuit.

what is the other side of the lamp connected to?

Ground.

5VAC -> lamp -> GND

NO idea then. But if your supply is doing something weird like that I suspect a fault in your ground wiring somewhere.

Cant really help much more. even if you get it working it is still going to cook.

Okay, well thanks for looking at it.

good luck