What is wrong with op-amps?

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#1,283
vacuphile said:
No discrete component has ever done that to me.
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Well, my mum trod on a resistor that had buried itself in my bedroom carpet with the wire poking up once. When I arrived home from school she greated me from my bedroom window (upper floor) and I watched as all my bedroom 'stuff' exited through the window and down onto the front driveway. Now I avoid doing my hobby in a carpeted room !
 
#1,285
Along with surface tension in the rapidly cooling solder blob and skin tension in the now-rapidly appearing blister. 🙁

(OUCH)

Likewise, I misread SY's comment about stepping on a tube--ouch. I read it as stepping on a tube (package) of DIP-8's. Carpets and electronics don't mesh, folks.
 
#1,290
The OPA124 (2134) is a pretty good workhorse op amp. I used it in the CTC Blowtorch for servos, in the Constellation phono stages for servos, and in the JC-3 for a line stage op amp. It is NOT a perfect OP AMP, but it is a pretty good one. It has low DC offset, decent slew rate, marginal low noise for a fet input op amp, and low cost. However, discrete can be better, and maybe several newer IC op amps might be better for a number of locations.
 
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#1,291
Kirchhoff said:
Since we weren't able to reach any conclusion, maybe we should try the opposite approach: look into what is NOT wrong with opamps :joker:
Or maybe we should look at them one by one? Let me start with stating that there is nothing wrong with OPA134.
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You would have to spend some time looking at its 'schematic'.

Semiconductors replacing actual resistors first to look for.

Then ultra high open loop gain, huge feedback to correct all of the non-linearities and *tiny* die size.

These tecniques used in semi mfg reduce costs and increase margins.

So the question becomes whose problem is being solved by using these devices?

I have not studied the OPA134 published topology, possibly it is a keeper.

-
 
#1,294
I think it was a typo and John was actually reffering to the OPA134 and OPA2134, as his comments are in line with his previous remarks here on these opamps.
I would also add that:
- they are available in PDIP too
- the price is reasonable
- they are readily available
- they do not need any design trickery

Yes, they don't win any spec sheet contests, but within their price category they are a reliable contender. As for those that implemented with them, they never found them "exquisite", but neither did they call them "dull", "compressed", "disarticulated", "unmusical", "weird" or some other word that would suggest that there is something "wrong" with them.
 
#1,295
Yes, I did think it a bit strange although two devices were mentioned so it couldn't be taken as a given that it was a typo... and in the event I see John has edited his post and still not got it fully correct 😉

So, OPA134 and OPA2134.
 
#1,296
jfetter said:
You would have to spend some time looking at its 'schematic'
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My thoughts are don't look at the schematics, they tend to be simplified versions anyhow and furthermore there are structures that don't have exact counterparts in the discrete world - there are tricks that aren't possible with discrete devices. It's a single piece of crytalline silicon shaped and sculptured to provide useful functions. Equivalent schematics are just an aid to understanding them. One day computers running smart software will design them with less and less human input.

Don't compare i.c.'s with discrete circuits - any more than you would compare solid state and valves.

Look at i.c.'s as a new monolithic lifeform, not as integrated versions of discrete circuits.

They require a different design approach and are fabricated differently. They have their own strengths and weaknesses. Design to their strengths, accept compromises as we do with discrete circuits.

Free your minds from the tyranny of comparison and embrace the possibilities:hypno2:
 
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