[NelsonVandal]

http://www.national.com/pf/LM/LME49713.html#Datasheet
A current feedback, super spec'd opamp from National. They call it an audio opamp! "Easily drives 150 Ohm loads". High bias current of course. I guess one has to use caps or a DC-servo. Anyone tried it or thinking of trying it? I'm very tempted, especially since I've heard TPA6120. Why is there so little love for current feedback opamps?

 

[TzeYang]

because despite their super fast bandwidth they are not as easy to apply as compared to conventional voltage feedback opamps.

/

On a side note, i believe the Jisbos is a very nice simple current feedback buffer.

 

[Mikemaxcel]

The LME49713 became very hot as I placed it onto my Sony CDP-557ESD audio buffer IC sockets that originally used 5534.I did try using AD844 (CF)with success.
Any comment?

 

[TzeYang]

Oscillation.

This is why swapping fast opamps are not recommended if you do not know how to deal with it.

 

[ROBSCIX]

Yes, high speed opamps can become unstable in certain circuits. They start oscillating and this draws excess current which results in excess heat.

All opamps will produce some heat, some more then others. If you can put your finger on the opamp and leave it there for 4-5 second that might be considered normal.
If the chip is so hot that you cannot even touch it, it is malfunctioning.

 

[jcx]

with CFA the feedback impedance is part of the frequency compensation so they shouldn't be used in op amp rolling - the circuit really has to be designed for them from the start
many Voltage feedback op amp circuits will have a feedback Cap - absolutely forbidden when using CFA
and typical feedback R values for VFA circuits are likely too high for good CFA compensation


the "best" op amp in my opinion is a multiloop composite amp with a good (fet input) VFA op amp up front and a CFA device with gain providing the high output current drive

Walt Jung has explained the benefits many times
http://waltjung.org/PDFs/ADI_2002_Se..._Drivers_I.pdf
1st section shows several multiple op amp composites, p27 fig 6.53 is the classic "Jung Multiloop"

 

[peranders]

Quote:

Originally Posted by NelsonVandal /img/forum/go_quote.gif LME49713 - High Performance, High Fidelity Current Feedback Audio Operational Amplifier Why is there so little love for current feedback opamps?

Lack of knowledge I should think. I have designed four current feedback headphone amps and _I_ love it. I have used TPA6120 and three discrete solutions. The trick is that you must forget parts of the theories you have learnt about normal voltage feedback amps and really study how a current feedback amplifier really works.