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| What is your favorite most versatile op-amp? |
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| MasterT:
--- Quote from: exe on June 09, 2019, 04:27:14 pm ---Isn't THD frequency-dependant? If so, can lm358 still be good for low-frequency signals? As for offset, why do you say it's not an issue? If DC accuracy is required, it is an issue. --- End quote --- It is affected by frequency, but it does not go to 0% (THD) at DC level. So, no, LM358 and NE5532 are not good above 12-bits. --- Quote from: Zero999 on June 09, 2019, 04:36:01 pm --- Noise can't be accounted for in software, so it's pretty important in my opinion. --- End quote --- Noise easy to null out by averaging in software. Though ADC sampling rate needs to be higher. --- Quote from: SiliconWizard on June 09, 2019, 04:35:02 pm ---One thing to note about the NE5532 is that (at least in the TI datasheet for the NE5532 that I have) there is no figure to be seen regarding distortion. Did I stupidly miss it? Does anyone have a datasheet stating distortion? And if we're going to use NE5532's made by TI, how are we going to know what to expect in terms of distortion? I've used the LME49720 with very good results for current-to-voltage output stages for audio DACs. --- End quote --- I love LME49721, pity charts depicted THD just to 6-7 kHz. NJM5532 has THD at page 3, THD vs. Output Voltage TI has data for NE5534, I'd think 32/34 as a twins. --- Quote from: exe on June 09, 2019, 07:16:29 pm ---Just don't make it sink :). I mean, if we are talking about ADC, crossover distortion is irrelevant, isn't it? --- End quote --- And this is most interesting parts. Interfacing to high resolution ADC is tricky, +-15V power is not applicable since next question would be safety of the ADC. Tweaking with high end adc (16 /18 bitters from TI and AD, ad7988, ad7984, ads8866) I came to conclusion that all worlds leaders failed to make R2R ultra low THD (0.0001%) OPA. AD on their AD7988 evaluation board, follow old fashion design - demanding -2.5 +7.5V power for OPA just to keep THD under control. So, crossover still in there, and it's not the only one of source THD to keep an eye on. |
| David Hess:
--- Quote from: MasterT on June 09, 2019, 11:39:53 pm --- --- Quote from: Zero999 on June 09, 2019, 04:36:01 pm ---Noise can't be accounted for in software, so it's pretty important in my opinion. --- End quote --- Noise easy to null out by averaging in software. Though ADC sampling rate needs to be higher. --- End quote --- If flicker noise could be averaged away, then there would be no need for chopping. |
| H713:
LM4562 has come down in price considerably over the last few years, so that has a considerable impact. I didn't realize just how much its price came down over the last few years. IMO, (again from an audio point of view), applications where a 5532 or 5534 is suitable, the LM4562 is probably a better choice, because if the relatively high current noise of a 5532 isn't a problem, the LM4562's even higher current noise may not be an issue either. Again, this really does come down to application. A microphone preamplifier has different requirements from an EQ circuit, and the digital world (which I don't deal with very much) will likely have different (in some cases more stringent) requirements. The discrete op amp is a great example. It seems foolish, after all it is a costly and large, and the DC precision is poor compared to even a 741. The noise performance and linearity, however, can be excellent, and they can be designed to handle very high supply rail voltages. For some applications it is a poor choice, but for others it makes perfect sense. Still, I think if one is going to make a list of good, versatile op-amps to stock, the LM4562 (not a whole lot more costly than a 5532 these days) and perhaps something like an OPA2134 would be on my list. With that said, there are a ton of comparably decent FET input op amps, some of which may or may not be relevant now. I still have a large stock of OPA604s and AD713s, but their cost makes them hard to recommend at this point over something like an OPA2134. Even the TL072 is perfectly adequate for many applications, and they're cheap as chips. |
| magic:
--- Quote from: exe on June 09, 2019, 07:16:29 pm ---Just don't make it sink :). I mean, if we are talking about ADC, crossover distortion is irrelevant, isn't it? --- End quote --- CMRR is still crap, though. --- Quote from: MasterT on June 09, 2019, 11:39:53 pm ---NJM5532 has THD at page 3, THD vs. Output Voltage --- End quote --- Damn, I missed it :palm: --- Quote from: MasterT on June 09, 2019, 11:39:53 pm ---TI has data for NE5534, I'd think 32/34 as a twins. --- End quote --- They aren't, 5532 has its open loop gain reduced to stay stable in voltage followers and it shows as more distortion at audio frequencies. Also lower unity gain frequency and slew rate. --- Quote from: MasterT on June 09, 2019, 11:39:53 pm ---I came to conclusion that all worlds leaders failed to make R2R ultra low THD (0.0001%) OPA. --- End quote --- OPA365 comes close by using internal charge pump to generate beyond-the-rails voltage supply for its input stage. Other similar opamps may exist, but most R2R input designs combine two input stages and have bad "input crossover" distortion. |
| RES:
LT6015 (SOT-23-5) https://www.analog.com/media/en/technical-documentation/data-sheets/601567ff.pdf |
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