Chip buffers

[jaycee]

Originally Posted by peranders

Not many pcb's are made with a native pcb software. I used a 15000 USD software the german RUN Electronic Design System. The software was a bit special, the only software in the world with "real"-annotation. The project was in a single file with 100% synchronisation between schematics and the layout and it happened in real-time. If I inserted a resistor in the schematics, boom you have a resistor in the pcb.

I am curious if you ever tried CadSoft EAGLE. It has synchronization between schematic and PCB's, and it also runs on Windows, Mac OS X and Linux. It also costs a lot less than $15000 as far as I know!

[peranders]

I have played with Eagle but I haven't done anything serious with it.

[analog_sa]

Originally Posted by zener_diode

Although not as good as the LME49600, it is still excellent for no feedback!

Having listened to the 634 open loop i think it really sucks. Not that i love it under a nfb loop but it's at least acceptable. Another illustration that these type of measurements are a complete waste of time?

[Andrea:]

Originally Posted by analog_sa

Having listened to the 634 open loop i think it really sucks. Not that i love it under a nfb loop but it's at least acceptable. Another illustration that these type of measurements are a complete waste of time?

I don't know...have you measured the BUF634 while working open-loop, too? This would be nice as we could put apples against apples

[Andrea:]

Originally Posted by zener_diode

At first, I didn't think I had any BUF634 chips laying around... but yes, I have a
couple.

All circuit connections are the same as with the LME49600 measurement.

At full scale, the THD+N is .0007%. Only slightly worse than the LME49600. It is
mainly 2nd harmonic as you can see in the plot (Spectrum3.pdf). With a 220
resistor, the THD+N gets slightly worse at .00085%. Again, an increase in 2nd
harmonic (Spectrum4.pdf). IMD was the same for both BW pin settings at
.0005%.

Although not as good as the LME49600, it is still excellent for no feedback!

Also, my baseline IMD is .0004%, not .0005% as I previously stated.

Ouch, I'd missed your reply! Alright, so the BUF634 holds its own. Good...because I recently got some free samples...


BTW, I think the only real advantage of the LME49600 probably is its package..

[zener_diode]

Originally Posted by analog_sa

Having listened to the 634 open loop i think it really sucks. Not that i love it under a nfb loop but it's at least acceptable. Another illustration that these type of measurements are a complete waste of time?

Thanks for pooping out your opinion without any supporting information.

Real measurements are never a waste of time as they provide hard evidence of
some performance criteria.

[zener_diode]

I did another measurement using a 10kHz sine. Only the 2nd, 3rd and 4th
harmonics can be viewed though (96kHz sampling).

Baseline = .00055% THD+N
LME49600 = .0015% THD+N
BUF634 = .0008% THD+N

Plots are attached.

[qusp]

I have read of problems with DC offset with the national chip (is there anything to this?), so I have stuck with using stacked BUF634 (HiC and 100R) when i'm not using peranders excellent discrete buffer SSR01 that is