I don't know if this is the right place to ask about opamps, but I'll try anyway:
Does anybody know how much current a NE5532 can supply on it's output? I guess it is about 20-50 mA or something like that, but I can't find any datasheet of the NE5532 stating that parameter. Nor does it say anything about maximum power dissipation.
Is it possible to calculate maximum output current by other parameters or do I have to make a test circuit that might destroy it?
I could use power opamps instead, but they seem to be expensive - even the smaller ones, that will supply up to 200 mA.
So, If anybody knows of some opamps similar priced to the NE5532 that can supply 50-100 mA or more, or at least states how much it can handle, I would be very happy to know about it. And - it has to be unity-gain stable, so I can use it as a voltage follower without problems.
Does anybody know how much current a NE5532 can supply on it's output? I guess it is about 20-50 mA or something like that, but I can't find any datasheet of the NE5532 stating that parameter. Nor does it say anything about maximum power dissipation.
Is it possible to calculate maximum output current by other parameters or do I have to make a test circuit that might destroy it?
I could use power opamps instead, but they seem to be expensive - even the smaller ones, that will supply up to 200 mA.
So, If anybody knows of some opamps similar priced to the NE5532 that can supply 50-100 mA or more, or at least states how much it can handle, I would be very happy to know about it. And - it has to be unity-gain stable, so I can use it as a voltage follower without problems.
The datasheet I have (TI) says typically the current limit is 38mA, but the minimum is 10mA. Doug Self has a paralleled NE5532 design working as a power amp, so you could do worse than to copy that and reduce the number of opamps to suit.
Yes, I know that design and it works extremely well for me in my headphone amplifier where I paralleled 8 NE5532 voltage followers for each channel. That's why I now want to do something similar in a power supply with power opamps or a lot of low power opamps like NE5532, to reduce noise and make a very clean and low impedance power source. It is all experimental and it might turn out to be a bad idea, but I have to try it.
So I guess if I need to supply 1 ampere with reasonable margins, so it should be able to deliver about 2 amps without breaking down, I need a whole lot of NE5532's. If I could get a similar priced opamp with min. output current about 50 mA or more, that would be very nice. I am very open for suggestions 🙂
So I guess if I need to supply 1 ampere with reasonable margins, so it should be able to deliver about 2 amps without breaking down, I need a whole lot of NE5532's. If I could get a similar priced opamp with min. output current about 50 mA or more, that would be very nice. I am very open for suggestions 🙂
the 5534 and many older op amps have very asymmetric output stages, performance can be really poor near one rail, less so at the other
I have measured a large increase in distortion near 1/2 fo the rated output current with some op amps - just because the short circuit rating is ~40 mA doesn't mean you get good performance there
paralleling for higher output current is "inefficient" for performance because you still have internal thermal feedback, power supply pin current coupling, and the N extra op amp's loop gain isn't adding to the feedback around the output stages
a better approach is to use a multiloop composite amplifier with a purpose designed high current output amp/buffer and your preferred good quality/low noise audio op amp for input servoing the output of the fast, high current output amp
the output amp/current buffer needs to be much faster than the input op amp to avoid stability compensation issues when including it in the input op amp feedback loop
CFA op amps make good high current outputs - heat removal becomes a problem at higher power - LT1210 is a 1A output 35 MHZ CFA op amp in a TO-220 package
extreme op amp heatsinking (6x TPA6120, paralleled and totem pole/cascaded in a multiloop with OPA627 input/overall feedback)
I have measured a large increase in distortion near 1/2 fo the rated output current with some op amps - just because the short circuit rating is ~40 mA doesn't mean you get good performance there
paralleling for higher output current is "inefficient" for performance because you still have internal thermal feedback, power supply pin current coupling, and the N extra op amp's loop gain isn't adding to the feedback around the output stages
a better approach is to use a multiloop composite amplifier with a purpose designed high current output amp/buffer and your preferred good quality/low noise audio op amp for input servoing the output of the fast, high current output amp
the output amp/current buffer needs to be much faster than the input op amp to avoid stability compensation issues when including it in the input op amp feedback loop
CFA op amps make good high current outputs - heat removal becomes a problem at higher power - LT1210 is a 1A output 35 MHZ CFA op amp in a TO-220 package
extreme op amp heatsinking (6x TPA6120, paralleled and totem pole/cascaded in a multiloop with OPA627 input/overall feedback)
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At 1-2 A that just doesn't seem sensible. You want an external pass transistor to get the heat away from the error amplifier part of the circuit. There's no advantage to having it all on one die. Output impedance will be determined more by the feedback arrangement than anything else. I do remember some small tab package opamps with a few hundred mA of output (LM759) but don't know what's currently available. You could get there with 3 or 4 of those if you just have to try it.
"similar priced to the NE5532"
This is a mission impossible.
There are very few OPamps in the class of NE5532 and similar price.
In fact, I don't know any!!!
Hi, I agree totally, for its price nothing gets near current wise (or anything else), rgd, sreten.
Thanks for your replies 🙂 Seems like my idea probably won't work, or will be very expensive, inefficient, break down because of heat issues or something like that.
I have thought about using one single power opamp or maybe 2 paralleled power opamps instead of a whole lot of NE5532's. It seems like some of the power op amps are specifically made for power supplies. Would that be a better idea? It might be cheaper as well, if I need 1-2 A. What about noise levels and output impedance? I know that paralleling NE5532 reduces noise and output impedance, and that's what I want. But I think I need too many of them to make 1-2 A and it will be hard to mount them on a heatsink compared to the power opamps in TO220-housing?
I don't know anything about multiloop composite amplifiers. Is that opamps coupled with discrete transistors with some kind of advanced feedback loop?
I have thought about using one single power opamp or maybe 2 paralleled power opamps instead of a whole lot of NE5532's. It seems like some of the power op amps are specifically made for power supplies. Would that be a better idea? It might be cheaper as well, if I need 1-2 A. What about noise levels and output impedance? I know that paralleling NE5532 reduces noise and output impedance, and that's what I want. But I think I need too many of them to make 1-2 A and it will be hard to mount them on a heatsink compared to the power opamps in TO220-housing?
I don't know anything about multiloop composite amplifiers. Is that opamps coupled with discrete transistors with some kind of advanced feedback loop?
composite amplifiers can use descrete or other IC amps to improve the performance over that of just 1 op amp
for application that fit in the supply rail range of integrated chip amps they are convenient
http://focus.ti.com.cn/cn/lit/an/sboa002/sboa002.pdf
http://waltjung.org/PDFs/ADI_2002_Seminar_Ch6_Audio_Drivers_I.pdf
you can combine ideas, if you just need 2x more than a otherwise adequate op amp's current then paralleling output current buffer amps can be practical
the 2 output chips can still be inside the feedback loop of a good quality audio input op amp
people have added a good quality op amp to a power chip amp (LM3886, TDA7293, ect. ), but it is a little more dificult to stabilize since many power audio chip amps are decompensated for minimum gain >10 already and are slow compared to today's better audio op amps
for application that fit in the supply rail range of integrated chip amps they are convenient
http://focus.ti.com.cn/cn/lit/an/sboa002/sboa002.pdf
http://waltjung.org/PDFs/ADI_2002_Seminar_Ch6_Audio_Drivers_I.pdf
you can combine ideas, if you just need 2x more than a otherwise adequate op amp's current then paralleling output current buffer amps can be practical
the 2 output chips can still be inside the feedback loop of a good quality audio input op amp
people have added a good quality op amp to a power chip amp (LM3886, TDA7293, ect. ), but it is a little more dificult to stabilize since many power audio chip amps are decompensated for minimum gain >10 already and are slow compared to today's better audio op amps
To make everything clear - I am trying to make a very low noise and low impedance power supply for any application requiring about 1 A or less. Maybe it is going to be an small signal AC "regenerator" or just a DC power supply. Maybe both. I don't know yet. But I'm NOT trying to drive a speaker - it is not an audio amplifier - it is going to be a power supply. That power supply could drive a headphone amplifier, a DAC, phono preamp or maybe something totally different - you name it, and in the case of hifi-equipment, I hope it will sound better than providing standard 12V or 24 AC directly from a transformer, or in the case of DC, better than a normal regulated LM317-based DC supply. It is all experimental and I don't care if it is not super efficient or a little expensive, as long as it is stable and safe etc.
So before everyone says - that won't work, or that's a bad idea or something like that - I want to find out myself - that's the way I learn and I'm only asking for advice because it could speed up the development and help me avoid the worst "no go"s.
And I think you guys are very helpful so far, but also a bit confusing to me 🙂 But I hope I have made it more clear, now, what I am trying to make 🙂
So before everyone says - that won't work, or that's a bad idea or something like that - I want to find out myself - that's the way I learn and I'm only asking for advice because it could speed up the development and help me avoid the worst "no go"s.
And I think you guys are very helpful so far, but also a bit confusing to me 🙂 But I hope I have made it more clear, now, what I am trying to make 🙂
Hmmm... well a practical consideration is that no matter how good the PSU is, once you add a few cm of wire and PCB print to the output things rapidly deteriorate. What is perfect at the PSU output is much less so down the line.
Learning by doing is the only way... I never just accepted anything on trust with electronics... always had to find out myself.
Have you considered "remote load sensing" whereby the resistance of the PSU output leads is compensated for by including them within the "error amp and feedback network". That's a common option on lab PSU's
An opamp and power transistor is as good an option as any as regards development work and experimenting with.
If you are serious about this then it's essential to use a scope and pulsed load to really test how a PSU behaves under dynamic conditions.
Edit, you will have to read the whole thread but this dives in at the middle with some real world tests of DIY PSU.
http://www.diyaudio.com/forums/powe...egulator-between-jung-flea-3.html#post1572675
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jan demonstrated this in part III of the AudioXpress articles (archived on Walt Jung's website Home) -- remote load sensing permitted the impedance of the supplies to be lowered into the microOhms.
For a good discussion of opamp capaility -- suggest the late Bob Pease's applicaton note AN-1485: http://www.national.com/an/AN/AN-1485.pdf
The Effect of Heavy Loads on the Accuracy and Linearity of Operational Amplifier Circuits (or "What's all this output impedance stuff, anyhow?")
That is interesting. I know that some of the power opamps I have read about actually has either remote sensing built in or very clear application notes on how to do it. I don't know exactly what it is, but I will check it out and see how it works 🙂
Thanks for the links as well - I will check that out too 🙂 Finally, I feel I'm getting somewhere with this project - that's great - Thanks a lot 🙂
Thanks for the links as well - I will check that out too 🙂 Finally, I feel I'm getting somewhere with this project - that's great - Thanks a lot 🙂
I would think a couple of BUF634 in parallel inside the feedback loop of your 5532 would get you all the output current you need at modest expense.. Make sure to heat sink things well. (A single one will give you up to 250mA if you can live with lower current capability.) Note that Darlings can also be used as pass elements, but will be much slower, you can also use mosfets...) The BUF634 offers short circuit protection which is a nice feature to have and excellent AC performance.
On the remote sensing thing be sure to sense both ground and supply at the load end of things, and buffer both sense lines..
Take a look at the LM4562 as a potential sub for the 5532, significantly better AC performance and DC accuracy.
BUF634: http://focus.ti.com/lit/ds/symlink/buf634.pdf
LM4562: http://www.national.com/pf/LM/LM4562.html#Overview
On the remote sensing thing be sure to sense both ground and supply at the load end of things, and buffer both sense lines..
Take a look at the LM4562 as a potential sub for the 5532, significantly better AC performance and DC accuracy.
BUF634: http://focus.ti.com/lit/ds/symlink/buf634.pdf
LM4562: http://www.national.com/pf/LM/LM4562.html#Overview
I am using a stack of 4 LME49710 -- the DIP version -- on each side of the "Rabbit Hole" preamp -- much better than the NE5534's.
In addition to the BUF634 you can also consider the LME49600 -- pretty remarkable buffer chips.
In addition to the BUF634 you can also consider the LME49600 -- pretty remarkable buffer chips.
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