BUF634P availability

[amb]

Be careful about using OPA551 as the output buffer on any circuit that wraps it in its feedback loop (i.e., Pimeta). The OPA551's bandwidth much less than that of BUF634, and such an application might cause instabilities.

 

[synaesthetic]

When using Sijosae's discrete buffers, what should R11's value be?

Also do they need to have something in R8?

I am building a cheapjack PIMETA with TREAD + generic wall wart (cheaper than an Elpac) for fun; trying to see how good I can make one sound with the cheapest decent components available. Should be a good DIY refresher for me as well as I haven't done this kind of work in a few years. I'd like to get back in the swing of things before tackling something bigger and expensiver. =D

 

[MrMajestic2]

Quote:

Originally Posted by synaesthetic /img/forum/go_quote.gif When using Sijosae's discrete buffers, what should R11's value be? Also do they need to have something in R8? I am building a cheapjack PIMETA with TREAD + generic wall wart (cheaper than an Elpac) for fun; trying to see how good I can make one sound with the cheapest decent components available. Should be a good DIY refresher for me as well as I haven't done this kind of work in a few years. I'd like to get back in the swing of things before tackling something bigger and expensiver. =D

R11 is not needed for those buffers. I think I read that mono put a resistor in R8, but I dont remember the value. Might have been for his modified Sijosae buffers.

 

[synaesthetic]

Do you need to change the relative values of Q1 and Q2 to bias the amp into Class-A using the Sijosae buffers?

 

[Pars]

Quote:

Originally Posted by MrMajestic2 /img/forum/go_quote.gif R11 is not needed for those buffers. I think I read that mono put a resistor in R8, but I dont remember the value. Might have been for his modified Sijosae buffers.

Mono put low value resistors in R8 to provide some short circuit protection, since the discrete buffers are unprotected.

 

[synaesthetic]

Would 100 ohm resistors in R8 be sufficient?

 

[Pars]

10 or less would be better, but you could try it and see if you can hear them or they decrease volume too much.

 

[synaesthetic]

Thanks. Resistors are cheap anyway so I'm not worried about the cost.

 

[peranders]

Quote:

Originally Posted by rickcr42 /img/forum/go_quote.gif The National LME49600 is the BUF634 "rebranded" with the only difference being the buffer package 8-Pin DIP & TO-220 for the BUF634 http://focus.ti.com/lit/ds/symlink/buf634.pdf TO-263 SMD for the LME49600 http://www.national.com/ds.cgi/LM/LME49600.pdf Maybe Brown dog will come out with the adapter

LME49600 is not identical to BUF634, better in fact.

 

[rickcr42]

Quote:

Originally Posted by peranders /img/forum/go_quote.gif LME49600 is not identical to BUF634, better in fact.

Have you actually compared the two ? Read the available data beyond the "hyped up" press in the trade rags ? compared the internal structures ?

For instance ;

The only difference in specs is the low bandwidth spec with the BUF634 being 30mHz at the low end and the LME coming in at 100mHz but at FULL bandwidth they are identical : 180mHz

Then we have ;

1-Power Supply Range-both +/- 2.5 to +/- 18 VDC

2-Slew Rate-both 2000V/uS

3-THD -Can not be compared "on paper' the BUF634 not providing the data

4-Output current-both 250mA

5-Listed Applications-IDENTICAL

6-Internal Structure-IDENTICAL

7-Current Limiting & Thermal Shutdown-IDENTICAL

8-idle Current-data inconclusive being very murky at best

conclusion ?

Same part,different package and label.No other way to look at the data and see it any other way.If you or anyone else has conclusive data showing it any other way i would be interested in seeing it

rick

 

[peranders]

I had information from a National guy that they weren't identical but performance wise they seem to be similar at least.

 

[rickcr42]

Quote:

Originally Posted by peranders /img/forum/go_quote.gif I had information from a National guy that they weren't identical but performance wise they seem to be similar at least.

Weak man.not even close to "conclusive" evidence

If by different the "National guy" means they are in different packages then on that level he is correct.If by different he means the low bandwidth spec is different then yes,he is correct.But to say they are not the same part is not correct from what i can tell and especially so if you actually look at the published internal schematic of both parts.

Hell man,even the damn parts values are the same !

It will take more to prove the difference,to undeniably show where the topology is NOT the same and so far I don't see anything even close


Rickster

 

[peranders]

Remember that the schematic is simplified. You don't see the whole truth. I think we can agree on that BUF634 can be replaced by LME49600 in many applications.

 

[Pars]

Unless National purchased a technology transfer from TI/BB for the 634 IP (unlikely) it would be hard to call it the same part. Every semicon manufacturer has their own die design/fab processes and while these can result in an equivalent part if that is the design goal (like LM317s between different manufacturers, for example) they are not identical down to the die level.

Interesting that National chose a completely different package than any TI has available in the 634... coincidence? Doubtful...