Spoilt for choice

Thread Starter

Wolframore

Joined Jan 21, 2019
2,317
Have you tried to shop for a new opamp for whatever reason? Digi-Key showed 24,270 results. Even with duplicate listing for packages and variants we are looking at a puzzling amount of choices. Then I started to narrow down some by voltage or rails...etc. regardless I feel like a lot of time is spent shopping.

I had a thought that while there are some challenges to designing circuits, so many circuits are now a bunch of chips strung together and wow it works. But when it doesn’t work, it’s a black chip like any other usually with no schematic... who knows if it’s working correctly or not.

Is it just me. I feel like the previous generation with less ICs had to understand, design and do more to achieve a good design. Ive seen some good design and some not so good stuff but they all took a lot of work to get there Im sure.
 

BobTPH

Joined Jun 5, 2013
3,475
My rule is I set the parameters I need, getting everything that matches or exceeds them, then sort by price. The lowest priced ones are the most popular and likely the most proven performers.

Bob
 

AlbertHall

Joined Jun 4, 2014
11,393
Have you tried to shop for a new opamp for whatever reason? Digi-Key showed 24,270 results. Even with duplicate listing for packages and variants we are looking at a puzzling amount of choices. Then I started to narrow down some by voltage or rails...etc. regardless I feel like a lot of time is spent shopping.
The same applies to diodes, transistors and now MOSFETs.
 

Thread Starter

Wolframore

Joined Jan 21, 2019
2,317
The same applies to diodes, transistors and now MOSFETs.
don’t get me started on MOSFETs. Having said that I finally decided on my SOT3 standard low voltage from the si23xx series to AO34xx series. Wow they are getting really good. For the N channel: RDS(ON) < 33mΩ (VGS = 4.5V) they’re good for up to 30V. I need to find some decent power MOS that are reasonable.
 

atferrari

Joined Jan 6, 2004
4,378
Have you tried to shop for a new opamp for whatever reason? Digi-Key showed 24,270 results. Even with duplicate listing for packages and variants we are looking at a puzzling amount of choices. Then I started to narrow down some by voltage or rails...etc. regardless I feel like a lot of time is spent shopping.

I had a thought that while there are some challenges to designing circuits, so many circuits are now a bunch of chips strung together and wow it works. But when it doesn’t work, it’s a black chip like any other usually with no schematic... who knows if it’s working correctly or not.

Is it just me. I feel like the previous generation with less ICs had to understand, design and do more to achieve a good design. Ive seen some good design and some not so good stuff but they all took a lot of work to get there Im sure.
When parametric search was not a reality yet, browsing the datasheets was maybe, even more overwhelming.
I still have the last hard printed datasheets I got for free from National Semiconductors with so many new R to R and CMOS op amps. Local availability made most of the decisions for you.
 

ronsimpson

Joined Oct 7, 2019
1,313
Local availability made most of the decisions for you.
For me "local" is anywhere FexEx goes. All the local stores are gone.
I like the search engines at DigiKey (most places have good engines). I can say I want R-R and most of the OP-amps drop out of the list. I choose package, and bandwidth and ..... Then I can have the parts listed in order of output current or supply voltage etc. Years ago I had hundreds of data books and that was had.
 

Audioguru again

Joined Oct 21, 2019
3,304
Most old teachers today say to use a 52 years old uA741 opamp. Then the students come here to the forum to ask why the circuit performance is so bad. Then somebody here says to use a cheap one like an LM358 without telling them how to inhibit the unused opamp and the poor performance of the opamp in their circuit.
 

Thread Starter

Wolframore

Joined Jan 21, 2019
2,317
My handful of 741's gonna beat you up... and the 358's gonna help (I got them for a class)... We need to use them up! They work fine in many cases but far from ideal. Would be fine as dusk to dawn comparator. For slow integral functions they'll do just don't push them. Would be poor choice for precision instrumentation.... seriously tho they can all go in the trash for all I care.
 
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Delta Prime

Joined Nov 15, 2019
1,051
Hello there :)
Then I started to narrow down some by voltage or rails...etc. regardless I feel like a lot of time is spent shopping.
Bite my shiny metal... oh wait a minute you remind me of someone "8-bit"! . I feel the same way about shopping on that interweb. Then I remember going through a thousand page component guide list before the invention of the interweb and my blood pressure goes down.
:D
P.S. your Avatar reminds me of my IEEE insurance policy
;)
 
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Thread Starter

Wolframore

Joined Jan 21, 2019
2,317
Hey just started looking at inexpensive opamps again... this one looks interesting as a general purpose anyone try it? It's a drop in for the 741 but better characteristics and less restrictions.
CA3140
 

AnalogKid

Joined Aug 1, 2013
9,283
That is another older part, but it is not a "normal" opamp. It uses a combination of MOSFETs and bipolar transistors, giving it characteristics that are different from other parts. Not in a bad way, just different. Primarily, it has an exceptionally high input impedance. thiat means that if you design a circuit around this part's unipqe properties, it won't necessarliy work with another part dropped into the same socket. Usually that is an issue when moving backwards through time - a circuit designed around a 1990's bipolar, voltage-feedback part can be expected to have worse performance when a 741 id dropped into the socket. But with the 3140, a *later* gen part might not do the job.

I have some because I've used them in the past, but I consider them a specialty item like a transconductance amp.

ak
 

Thread Starter

Wolframore

Joined Jan 21, 2019
2,317
I like transconductance amps for certain uses... haven't figured out all applications yet... I noticed the PMOS front end... very interesting current sink design... thanks for heads up. High input impedance is nice in my book. Is it rail to rail... was looking but didn't see it.
 

atferrari

Joined Jan 6, 2004
4,378
Hey just started looking at inexpensive opamps again... this one looks interesting as a general purpose anyone try it? It's a drop in for the 741 but better characteristics and less restrictions.
CA3140
When I finally decided to understand how the different basic topologies actually work, I used de CA3140 with +-9V PSU.
Implemented them in a protoboard with very good results. Measurements of all currents involved came pretty consistent.

When designing a PID control from scratch, used them extensively and successfully managed to null the output offset as per the datasheet recommendations.

Following some of the usual suggestions from Audioguru I bought also a huge bunch of TL072 for eventual applications requiring low noise.
 

Thread Starter

Wolframore

Joined Jan 21, 2019
2,317
TL072's are good, they have FET front end. I get nervous about flipping polarity... Was your PID completely analog?
 
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