Genuine OPA828? You may want to read this, from https://www.ti.com/ordering-resources/distributors.html
LCSC themselves do not even list TI on their line card. In fact, TI does not list LCSC as a distributor.
Also, TI sells them directly to end users at only $6 for one.
Semiconductor products purchased outside of TI’s authorized distribution network, including through brokers, independent distributors, or online marketplaces (sometimes referred to as the “gray market”), may be counterfeit, modified, beyond TI’s recommended shelf life, or improperly stored or handled. Accordingly, TI does not provide warranty coverage or customer support for semiconductor products purchased outside of TI’s authorized distribution network.
Aside from transacting directly with TI, including purchasing directly from TI.com, customers have the following options to do business with TI:
LCSC themselves do not even list TI on their line card. In fact, TI does not list LCSC as a distributor.
Also, TI sells them directly to end users at only $6 for one.
Authorized distributors
Texas Instruments is committed to delivering high quality and reliable semiconductor solutions. We select our authorized distributors to meet these standards, and strongly encourage you to purchase all TI semiconductor products either directly from TI or from our authorized distribution network.Semiconductor products purchased outside of TI’s authorized distribution network, including through brokers, independent distributors, or online marketplaces (sometimes referred to as the “gray market”), may be counterfeit, modified, beyond TI’s recommended shelf life, or improperly stored or handled. Accordingly, TI does not provide warranty coverage or customer support for semiconductor products purchased outside of TI’s authorized distribution network.
Aside from transacting directly with TI, including purchasing directly from TI.com, customers have the following options to do business with TI:
- Arrow Electronics, in all regions except Japan
- Digi-Key Electronics
- Mouser Electronics
- Tokyo Electron Device (TED), exclusive to Japan
- Macnica, exclusive to Japan
- Spirit Electronics, an authorized small business reseller for Aerospace & Defense customers
- Rochester Electronics*, for obsolete or surplus TI semiconductor products
- Micross*, for wafer and die products
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There is a little mention of the ADA4625 on the forum, I recently tried it as an I/V conversion and I was amazed by the sound quality, almost like a CFA op amp. And as for OPA1641, the better choice is ADA4610, the price may be a little higher, but it justifies the investment. There is also a direct answer from AD to OPA627, namely ADA4627/4637 but I have never tried them.
We're now in Chip Amps, which is under Amplifiers (clearly short for POWER amplifiers, things meant to drive loudspeakers). Chip amps are one-chip devices with enough power output to drive speakers - the Chip Amps forum is for discussing them and building (power) amplifiers that use them.
I looked, there are some individual op-amp threads in Analog Line Level, but there is also op-amp discussion in Parts under Design & Build.
This old thread, using lots of op-amps in parallel to drive a speaker, could have perhaps gone in either one...
https://www.diyaudio.com/community/threads/doug-selfs-ne5532-power-amp-thoughts-anyone.174540/
Looking back at history, I have been discussing op-amps (and gain clones) in the chip amp section for 19 years. I would say that chip amps are definitively op amps (simply in large packages), and one could argue that low-powered op amps are technically chip amps as well because they are amps that are "chips," instead of SS discrete or tubes. But I get your point in drawing a line based on power output. I think historically gain clone/gain card came first, then people here decided to stay away from the copycat reference by calling the design "chip amps". Remember the old chipamps.com by Brian?
I however always treated "parts" as more passive in nature (e.g., resistors, caps). But again taking a step back, anything that is not a wholesome package is by definition a part.
Rings my alarm bell too much
Yeah, I accept and live by policy that any Chinese parts source is not to be trusted until proven otherwise. This was one-time purchase, last year during shortage when even TI had zero stock. Parts are absolutely confirmed to be 100% genuine, so LCSC is off my list of shoddy Chinese companies.
Yup, 100% genuine, confirmed by detailed application circuit measurements, where results are tightly related to opamp gain/phase curves and noise density over frequency. Absolutely identical as the other circuit with OPA828 from Mouser.
Anyway, there are many reputable distributors that carry TI parts stock, while not being on their distributors list.
I purchase almost exclusively from Mouser and TME (EU distributor) but wouldn’t hesitate to purchase from LCSC if there is no other source for the required part.
If you run into any issues with your parts TI won't provide technical support unless parts were purchased from TI distributors. Same with other manufacturers.
I think "Equipment & Tools" is the right topic...
OP mudihan, please forgive me for being off-topic temporarily.
The oscillator is a 6-point spot oscillator of 20, 100, 1k, 6.3k, 10k, and 20kHz.
The distortion meter part of the analyzer consists of a notch filter (Twin T) tuned to those frequencies.
The handwriting is ugly, but here is a simplified block diagram of distortion meter part .
Three stages of twin T are stacked so that attenuation of 150dB or more can be obtained even if the frequency of the oscillator or the notch frequency of the twin T drifts due to temperature changes. (Amplified by 26dB after the first-stage twin T.)
This removes the fundamental wave.
After that, it is amplified by 20dB, and 100kHzLPF (3rd order), 20kHzLPF (11th order brick wall), A filter can be selected, and then it is amplified by 20dB.
In other words, the harmonic components removed the fundamental are amplified by 66dB and output to Mon Out.
When the harmonic signal is large, the attenuator of S2 operates and becomes the amplification of 26dB.
Bottom left is the path of the input signal. When the input signal is large, it is amplified by -34dB, and when it is small, it is amplified by +6dB and output from IN MON.
It can calculate the distortion factor by taking AC RMS measurement of these two signals with Analog Discovery and dividing them by considering the amplification (attenuation) of each.
The bottom right circuit sums these two outputs and outputs to ANALISIS.
Assuming all the switches are arranged like this block diagram, the input signal (which can be thought of as the fundamental) is attenuated by -34dB and the harmonics are summed with the signal amplified by 66dB, so ANALISYS outputs a waveform with 100dB distortion emphasized. FFT this signal with Analog Discovery and measure it with the THD measurement function. Subtract the 100dB boost from this value to get the true THD. This enables ultra-low distortion measurements even with low resolution FFT functions.
By the way, when I saw the circuit diagram for the first time in a while, I noticed that this adder has a jumper pin. And when the short plug is set to the 30kΩ side, the distortion signal is attenuated by -20dB and added. On this side...
I completely forgot about it.
8 years ago me, great!
OP mudihan, please forgive me for being off-topic temporarily.
About eight years ago, I designed and manufactured a low-distortion oscillator and an Analyzer mainly for distortion measurement.
The oscillator is a 6-point spot oscillator of 20, 100, 1k, 6.3k, 10k, and 20kHz.
The distortion meter part of the analyzer consists of a notch filter (Twin T) tuned to those frequencies.
The handwriting is ugly, but here is a simplified block diagram of distortion meter part .
Three stages of twin T are stacked so that attenuation of 150dB or more can be obtained even if the frequency of the oscillator or the notch frequency of the twin T drifts due to temperature changes. (Amplified by 26dB after the first-stage twin T.)
This removes the fundamental wave.
After that, it is amplified by 20dB, and 100kHzLPF (3rd order), 20kHzLPF (11th order brick wall), A filter can be selected, and then it is amplified by 20dB.
In other words, the harmonic components removed the fundamental are amplified by 66dB and output to Mon Out.
When the harmonic signal is large, the attenuator of S2 operates and becomes the amplification of 26dB.
Bottom left is the path of the input signal. When the input signal is large, it is amplified by -34dB, and when it is small, it is amplified by +6dB and output from IN MON.
It can calculate the distortion factor by taking AC RMS measurement of these two signals with Analog Discovery and dividing them by considering the amplification (attenuation) of each.
The bottom right circuit sums these two outputs and outputs to ANALISIS.
Assuming all the switches are arranged like this block diagram, the input signal (which can be thought of as the fundamental) is attenuated by -34dB and the harmonics are summed with the signal amplified by 66dB, so ANALISYS outputs a waveform with 100dB distortion emphasized. FFT this signal with Analog Discovery and measure it with the THD measurement function. Subtract the 100dB boost from this value to get the true THD. This enables ultra-low distortion measurements even with low resolution FFT functions.
By the way, when I saw the circuit diagram for the first time in a while, I noticed that this adder has a jumper pin. And when the short plug is set to the 30kΩ side, the distortion signal is attenuated by -20dB and added. On this side...
THD can be measured without this happening!With OPA827 and OPA627, the second harmonic (40kHz) was larger than the fundamental wave of 20kHz, and 40kHz was regarded as the fundamental wave, so THD could not be measured.
I completely forgot about it.
8 years ago me, great!
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Impressive test equipment.
And impressive test results with the OPA828.
It could be interesting to see the distortion with a source resistance of e.g., 10k.
Unfortunately the noise of the OPA828 is relatively high, compared to the best bipolar op-amps.
Hopefully TI can one day "combine" the OPA828 with the JFE2140 for a really low noise JFET op-amp.
It would also be interesting to measure the performance of the ADA4898.
And impressive test results with the OPA828.
It could be interesting to see the distortion with a source resistance of e.g., 10k.
Unfortunately the noise of the OPA828 is relatively high, compared to the best bipolar op-amps.
Hopefully TI can one day "combine" the OPA828 with the JFE2140 for a really low noise JFET op-amp.
It would also be interesting to measure the performance of the ADA4898.
I collect data individually with G=+1, Input level=5Vrms for the common-mode distortion caused by the signal source impedance.
Older JFET op amps paled in comparison to bipolar except for the OPA627 which has a cascode bootstrap. However, BB(TI) products since the new OPA827 have improved significantly.
I am not familiar with the physical properties and process technology of semiconductors, but it may be due to silicon germanium.
OPA827 and OPA1641 are excellent when Rs is high, but OPA828 is superior when Rs is 3kΩ or less. I
This is the range when using a 10kΩ pot. I think that it will be the best for amplification after zoning
Hi jean-paul, After all OPA828? I'm also waiting for SOP (probably HSOP if it's released).
I had previously taken data of ADA4898, but because it was measured by FFT that emphasized the 100dB distortion rate, 40kHz was regarded as the fundamental wave and THD could not be measured.
So I switched the jumper pin mentioned in post #33 to the 30kΩ side and remeasured as 80dB emphasis.
ADA4898-1
Cyan is 5V/div, yellow waveform is 100 µ/div.
(344.17mV/154.02mV) * 0.001=0.00223%
80db emphasis, so THD=-93.059dBc=0.00222% (almost same as above)
AD (including LT) has not yet been released that surpasses the AD797 in measurement under this condition.
For audio applications, low voltage noise OPAMPs like the ADA4898 are suitable for MC head amplifiers.
In this case, the output level is at most 100mV, so the distortion is sufficiently small (even if the load resistance of the feedback circuit is low). So I think noise is more important.
Among op amps with 0.9nV/√Hz noise, only dual type is available so it is possible to create a stereo channel with one, or use it in parallel to achieve even lower noise easy.
I'm sure there are people who are interested, so I'm attaching the data I measured for the noise density of an OPAMPs with a spec of 0.9nV/Hz (@1kHz).
Shows the measurement circuit.
In the subsequent circuit, adjust the total gain to 120dB across a 20kHzLPF (11th brick wall).
Therefore, 1mV/√Hz corresponds to an input referred noise density of 1nV/√Hz.
The rise around 20kHz is due to aliasing from the LPF (which was used for CDP in the days when there was no digital filter oversampling) decay start slightly above 20kHz.
AD797
ADA4898-1
LT1028
LT1115
LME49990
Repeatedly, pity for the discontinue.
I made a small adapter for HVSSOP to DIP 8 including thermal pad for the 2828. It was a challenge to get it soldered. The sound of this OPAMP is indeed bliss, and extremely neutral with a very wide soundstage. I can understand why people, like the 627, might feel it sounds 'thin'. It's very, very transparant with lots of micro detail, yet it doesn't hurt your ears. Not a hint of sybilance when decoupled properly.
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