Amazing opamp measurement shoot-out - Page 2

andy_c · 4th September 2008, 03:45 PM

This reduces the feedback, which increases the distortion so that it's above the residual of the test equipment.

lumanauw · 4th September 2008, 04:31 PM

Since the noise is magnified 60dB, will it interfere with the measurement, like in FFT?

forr · 4th September 2008, 04:40 PM

I was interested by the bootstrapped current mirror in the one stage topology mentionned in appendix B. Are there discrete implementations of it ?

andy_c · 4th September 2008, 04:44 PM

Quote:

Originally posted by lumanauw
Since the noise is magnified 60dB, will it interfere with the measurement, like in FFT?

Well, the noise will get worse, but according to his text, he imports the raw data into the MATLAB program and does a bunch of averaging and filtering to reduce it. I gather the noise is less of a problem than the residual distortion of the AP System 1.

Wavebourn · 4th September 2008, 04:56 PM

Quote:

Originally posted by syn08

There are a few very strong contenders for the first place that were not yet evaluated:

OPA211, THS4031, OPA827, OPA2822, OPA842 from TI
ADA4899-1, AD823, AD8066, AD8610, AD8599 from Analog Devices
EL2227 from Signetics/Elantec

...and probably more...

...5562, CA3140. The last one has an excellent for audio output stage, but noisy input.

syn08 · 4th September 2008, 05:02 PM

Quote:

Originally posted by Wavebourn

...5562, CA3140. The last one has an excellent for audio output stage, but noisy input.

CA3140 - I have evaluated a few samples from Signetics and I was not happy with. The output stage might be very good, but it's a slow opamp, to slow to avoid slew rate induced distortions.

5562 - What is this?

Wavebourn · 4th September 2008, 05:29 PM

Quote:

Originally posted by syn08

CA3140 - I have evaluated a few samples from Signetics and I was not happy with. The output stage might be very good, but it's a slow opamp, to slow to avoid slew rate induced distortions.

In applications where I use them 15V/uS is enough.

Quote:

5562 - What is this?

Oops... Sorry for the typo, I mean 4562

syn08 · 4th September 2008, 05:47 PM

Quote:

Originally posted by Wavebourn

In applications where I use them 15V/uS is enough.

Oops... Sorry for the typo, I mean 4562

LM4562 is (AC) identical to the already tested LME49860. The slightly higher supply voltage allowed by the LME49860 is most likely the result of sorting the chips.

scott wurcer · 4th September 2008, 05:54 PM

This explains a call I got the other day. Did anyone notice the unbiased and unbypassed 6800uF caps in the test circuits?

lumanauw · 4th September 2008, 06:13 PM

Quote:

Did anyone notice the unbiased and unbypassed 6800uF caps in the test circuits?

Unbiased, do you mean the + of the 6800uF should be more positive than the - of the 6800uF? How can we do it in a simple cct?

4th September 2008, 05:54 PM	#19
scott wurcer diyAudio Member Join Date: Jan 2004 Location: cambridge ma	This explains a call I got the other day. Did anyone notice the unbiased and unbypassed 6800uF caps in the test circuits? __________________ Clay is embedded in our subconscious. It has been there for at least 50,000 years.

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4th September 2008, 03:45 PM	#11
andy_c Banned Join Date: Apr 2003	This reduces the feedback, which increases the distortion so that it's above the residual of the test equipment.

4th September 2008, 04:31 PM	#12
lumanauw diyAudio Moderator Emeritus Join Date: Oct 2002 Location: Bandung	Since the noise is magnified 60dB, will it interfere with the measurement, like in FFT?

4th September 2008, 04:40 PM	#13
forr diyAudio Member Join Date: Dec 2004 Location: Next door	I was interested by the bootstrapped current mirror in the one stage topology mentionned in appendix B. Are there discrete implementations of it ?