Need help finding an op-amp that suits my specifications

[Plecto]

Hi. I'm looking for a high-power op-amp. It's going to be used as a headphone amplifier so it needs to be able to output maybe 100mA at close to rail voltage. I've tried both the LM386 and the NE5532. The NE5532 seemed perfect, the only limitation was the output power. The LM386 had power, but I wasn't happy with the pre-set gain of 20. I also didn't like that I needed two chips for stereo and the zobel network on the output. I was more happy with the sound quality of the NE5532 aswell.

So. I wan't a dual op-amp just like the NE5532 only with more current and power output. A high supply voltage is also nice, I would say a minimum of +-10V (so I can safely use 2x9V batteries). An amp that comes with both SOIC-8 and DIP8 would be ideal. Future plans is to use SMD parts for this, but I would love to have a DIP-8 package aswell so I can replace my NE5532 chips.

I have also looked at the TPA6120. This seems absolutely ideal, but I would wan't something thats easier to handle (for now). The TPA6120 seems so fragile when it comes to oscillation, it also can't run from a virtual ground solution and it needs resistors on both the output and input. I feel that I don't know enough about electronics to start tackling this amp just yet, I'm afraid it could start coughing without me beeing able to fix it So an op-amp that doesn't oscillate easly would be best for now.

Edit: I would also like to figure out how I can see how much power an op-amp can output. I can find "short circuit current" in the datasheet, but I doubt this is the one to look for.

 

[sky_123]

Re: Need help finding an op-amp that suits my spesifications

You could use multiple NE5532's if that's what you're comfortable with.

 

[Plecto]

Re: Need help finding an op-amp that suits my spesifications

You could use multiple NE5532's if that's what you're comfortable with.

Like parallel connect them? Will that really produce a nice result?

 

[sky_123]

Re: Need help finding an op-amp that suits my spesifications

Apparently so. The author has a very good reputation for audio design, at any rate.

 

[Plecto]

Re: Need help finding an op-amp that suits my spesifications

If putting two LM5532's in parallel works, I guess that would be a fine solution, but I must admit that using just a single op-amp would be more delicate

 

[Plecto]

Re: Need help finding an op-amp that suits my spesifications

About this using two NE5532's in parallel. I saw the circuit that was linked, but it seems that that design is slightly different than mine. By parallel, is it meant that I connect every pin from one op-amp to the coresponding pin to the other op-amp? Or does it mean two seperate amps with seperate components and then just connect the outputs and inputs together? In the schematic linked I saw 1Ohm resistors from the output of every op-amp, do I have to perhaps introduce some extra components to this mix?

 

[FvM]

Re: Need help finding an op-amp that suits my spesifications

Paralleling must be done like in the link, keeping separate feedback and add output series resistors. Otherwise the outputs will short each other and small offset voltages can cause large output currents with saturation. Sufficient decoupling capacitors must be provided as well.

Although paralleling many NE5532 will surely achieve good quality, there are modern audio power amplifiers available that give similar (or even better performance) with a single device.

 

[Plecto]

Re: Need help finding an op-amp that suits my spesifications

there are modern audio power amplifiers available that give similar (or even better performance) with a single device.

This is exactly what I'm after. Could you name a type of chip? A chip that comes in both a dip-8 package and a soic-8 package would be ideal for me as it's kind of hard doing testing and prototyping on a soic-8 package. Price is also a factor all though not a huge one.

 

[FvM]

Recent high performance audio amplifiers like TPA6120 have very high bandwidth and require good circuit layout. A possible candidate with more regular parameters, also comming in DIP package would be OPA551.

 

[Plecto]

The OPA551 seems very nice. High enough supply voltage and output current by far, but the price seems heavy. Digi-key has them for 4.41USD, thats 9 USD to get both channels. As I mentioned in the opening post, the goal is to make an amp with the TPA6120, an amp that costs 6.7 USD. I would wan't something cheaper than the TPA6120 with two op-amps in one package so it can easly replace a NE5532. The LM386 is dirt cheap and very powerfull so couldn't there be a dual op-amp chip out there that is sort of between the LM386 and the NE5532 and still cost about the same as they do? I'm not that experienced with this so I don't quite know what I'm asking of, perhaps this doesn't exist?

Recent high performance audio amplifiers like TPA6120 have very high bandwidth and require good circuit layout.

I quick question about this. Theres only so much that can be done with the traces on a PCB (I can't do two layers), so other than adding a ground plane and making my SMD resistor kiss the pins of the chip, what else can be done? I feel I'm getting more and more terrified of this TPA6120 amp I was hoping that this amp will have a 0% chance of oscillating if I use SMD resistors close to the pins.

 

[FvM]

LM1877 should fit your requirements. Stereo 2x2W, DIL14 (obsolete but possibly still available) or SO14, cheap, moderate THD numbers, single supply. www.ti.com/lit/ds/symlink/lm1877.pdf

 

[Plecto]

I feel very picky here, but the LM1877 does not fit my requirement. Even if I was able to find a DIP14 package, a DIP8 would still be alot more neat. I see that the LM1877 can run off a split supply, but how does it like a virtual ground made with a resistor divider? It also uses more components with caps and resistors in parallel with the load and a cap from the inverting input to ground. This amp is made for driving 8 Ohm loads, how does it like driving 100-200 Ohm loads?

I will list my requirements for the amp I'm after (if it exist):
Same pin-out as a NE5532
Comes in a DIP-8 package
Minimum voltage supply of +-10V
Possiblity to give 200mW into a 62Ohm load
Does not oscillate easly
Can be put in the circuit pictured below:

**broken link removed**

 

[FvM]

I feel very picky here, but the LM1877 does not fit my requirement. Even if I was able to find a DIP14 package, a DIP8 would still be alot more neat. I see that the LM1877 can run off a split supply, but how does it like a virtual ground made with a resistor divider? It also uses more components with caps and resistors in parallel with the load and a cap from the inverting input to ground. This amp is made for driving 8 Ohm loads, how does it like driving 100-200 Ohm loads?

I think you have serious problems in understanding datsheets.
I'm out of here.

 

[Plecto]

Don't see the point of responding like that, I didn't know there was a minimum knowledge requirement or datasheet reading skills in order to post here.

I think I've found something that could work though, the LM4562 and the LME49860. It seems to fit my requirements. The only thing I don't know is how easy it oscillates, but giving it's a DIP8 package the external components are bound to have some distance to the chip, and the datasheet doesn't mention as much about oscillation preventions as the TPA6120 datasheet does.