What opamp number for :

[frank_p]

High-medium current, low frequency, relatively low voltage (less than 30V) and some relative precision in the output voltage ?
Bipolar would be great too.  Is there any kind of jellybeans that can do that ?

[Mike Burgundy]

Searching the right part is half the journey.
That said - to you these parameters might be very good since you have an idea of where you're going, but for outsiders hard numbers work best. Low frequency? Do you mean audio, or do you mean it's suitable to go down to xx Hz in a *certain* circuit?
There are supplier sites that let you select opamps base on xxmA pin current, power supply, slew rate, etc by hard numbers, maybe try one of those?

[merlinb]

The NE5532 / LM833 is an exceptionally good BJT opamp for the money, and relatively high current.
The other popular choice around here is the 4558 which is BJT, but not as powerful (which is good where battery life is concerned!)

[frank_p]

Searching the right part is half the journey.
That said - to you these parameters might be very good since you have an idea of where you're going, but for outsiders hard numbers work best. Low frequency? Do you mean audio, or do you mean it's suitable to go down to xx Hz in a *certain* circuit?
There are supplier sites that let you select opamps base on xxmA pin current, power supply, slew rate, etc by hard numbers, maybe try one of those?

Frequency: like a phaser LFO
Voltage rails: -12 +12 V or a bit more
Current: max 5 Amps ?  
Precision output: just for kicks, study and experimentation.

The NE5532 / LM833 is an exceptionally good BJT opamp for the money, and relatively high current.
The other popular choice around here is the 4558 which is BJT, but not as powerful (which is good where battery life is concerned!)

I want to built a big LFO in a huge box.
I don't think I will be ready for the 1000 contest.  

I don't need a fast opamp.
It's not an opamp anymore... Hein ?  ... It's a drive ?  ... A current source ?
I am all ears.

[DiscoVlad]

Frequency: like a phaser LFO
Voltage rails: -12 +12 V or a bit more
Current: max 5 Amps ?  
Precision output: just for kicks, study and experimentation.

If it's just for experimentation, just use the cheapest, then it won't matter if you burn some up.

741, 1458, 4558, and whatever the quad version of this for BJT opamps, TL071/2/4 for JFET input.

5 Amps output... good luck with finding an opamp which can sink/source that much current affordably.

OPA541 maybe? http://www.mouser.com/Search/Refine.aspx?Keyword=opa541 - several dollars, vs a few cents for the ones mentioned before.
You'd be better off using an opamp to drive a (darlington might be better?) BJT emitter follower there.

[frank_p]

If it's just for experimentation, just use the cheapest, then it won't matter if you burn some up.

I meant that if the output is relatively precise is not my main goal necessarily.

[DiscoVlad]

relative to what?

[frank_p]

relative to what?

Ideal tension source ?

OPA541 maybe? http://www.mouser.com/Search/Refine.aspx?Keyword=opa541 - several dollars, vs a few cents for the ones mentioned before.

Aouw man... I want it so bad !  Aouw !  25 $

[frank_p]

You'd be better off using an opamp to drive a (darlington might be better?) BJT emitter follower there.

Something like this on the output...  hmm...



...

Aww... I only have pnp power and medium power BJT in my drawers for this evening.   

[DiscoVlad]

Kind of, I was thinking something like the circuit down at the bottom of this page.
http://www.ecircuitcenter.com/circuits/pushpull/pushpull.htm

I would also recommend reading and working through the transistor and opamp all of the chapters of the The Art of Electronics.

[frank_p]

Kind of, I was thinking something like the circuit down at the bottom of this page.
http://www.ecircuitcenter.com/circuits/pushpull/pushpull.htm

OK OK Thanks.  That is good starting roads.   

I would also recommend reading and working through the transistor and opamp all of the chapters of the The Art of Electronics.

It's on my shelf.
I don't want to read it all tonight Vlad: I want to choose one battle or I'll make a burnout.