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What is your favorite most versatile op-amp?

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David Hess:

--- Quote from: maxwell3e10 on May 07, 2019, 11:58:28 am ---Many of these precision parts, like LT1012 and LT6012 have terrible slew rates, so while they maybe good for precision DC applications, they are not good for any dynamic application. A good general chip will not be ideal for any application (not lowest noise or highest slew rate or lowest distortion), but will be pretty good for all of them.
--- End quote ---

That is a common theme which applies across all parts.  The emitter or source degeneration of the input differential stage has to be minimized to provide high precision.  But this results in high transconductance which ultimately limits slew rate.  JFET and CMOS transistors inherently have lower transconductance so result in higher slew rates but lower precision.

This really shows up with "video" operational amplifiers which add resistive degeneration raising the slew rate but also lowering precision.  An early example of this is the 318 which has a 15 MHz gain-bandwidth product and 70 volt/microsecond slew rate.  These same parts have higher current output stages to drive 100 or 150 ohm loads but with their lower precision, this is acceptable.

The LM6171 uses a different topology which does not suffer from this limitation and is much faster but it requires a complementary process and matching between complementary devices compromises precision.  I have designed audio amplifiers with a similar topology.


--- Quote ---What do you think about OPA2189? It seems to have better specs than any other chopper op-amp I have seen?
--- End quote ---

Its specifications are better than any I have used.

Chopper stabilized operational amplifiers can be tricky to apply however.  Watch out for its input current noise which looks to be 75 times greater than an old "noisy" LTC1151.  That is consistent with larger area input transistors for lower voltage noise.  Chopper stabilized amplifiers should be used with low AC impedances limiting their versatility; they are not general purpose parts.

Pretty much if you do not have a big feedback capacitor and a big capacitor from the non-inverting input to ground, then you are using the chopper stabilized amplifier wrong.

maxwell3e10:
I tested OPA2189 dynamic characteristics at high frequency. It works pretty well, with a slew rate of 20V/usec and clean response. See below a comparison of 3 op-amps, each driven by a 16Vpp square wave. The frequency of the wave is 500 kHz (330 kHz for OPA2132).

I was looking for some weird effects associated with the chopper modulation. What I found is that for a non-inverting gain of 100 if the frequency of the sine is exactly 67.5 kHz, the gain has a periodic modulation. This only happens in about 1 kHz range, must be some interference effect with the chopper frequency.

Also OPA2189 is sensitive to high-impedance path on the input due to current injection, as others have also pointed out. This can lead to rather large offsets that depend on the capacitance, so one has to be careful to realize uV stability. When that is not crucial, then OPA2197 looked pretty nice and also inexpensive.

Gyro:
This is the second of these 'best op-amp for everything' threads in the past couple of weeks (https://www.eevblog.com/forum/chat/favorite-op-amp/msg2342253/#msg2342253). I don't get it - surely the op-amp you want is the one that's best suited to the specific application. If you try a 'one size fits all' approach then there are going to be massive compromises in all but the most mundane application.

You need to look closely enough at the datasheets to spot hidden 'undesirable features' is tricky enough as it is. Maybe a what's your favourite high impedance, DC precision, fast slew rate, high output drive? might have some value, but even then, there are all sorts of requirement combinations that would lead to a non-optimal match.

A parametric search is the only way to do it properly. That's what I would advise the OP to do for each of his applications.

Trying to tie down to one 'favourite' is just silly.

.... It would ultimately save the manufacturers the effort of producing many different parts though.

MarkF:
Maybe the title should read "Op-amp Short List"

It would be nice to have a list of a dozen op-amps to pick from for general use.
There are soo many available that it's overwhelming.

Gyro:
Agreed, that would be of more value, particularly if done by category.

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