Putting together a good assortment of op amps - Page 1
Forum section: electronics / beginners

author: zrlopez
author_rank: Contributor
timestamp: August 09, 2020, 07:32:35 pm
content: Hey everyone, I'm new here. Recently, I've been trying to design my own simple FM radio circuit and a possible power supply. I saw some designs that used an LM386 op amp, while for power supplies I've seen the LM317 be pretty popular. None of this mattered to me, because I realized that all I had to work with were some 8-bit shift registers and some LM311's. This got me thinking: I'm wanting to work some future projects involving power electronics and audio electronics. What are say, three MUST-HAVE basic op amps to have for working on audio and power? I'm having a hard time picking apart some basic ones I can have in bulk in my shop

author: ceoxrad
author_rank: Regular Contributor
timestamp: August 09, 2020, 08:18:50 pm
content: It all boils down on your particular interest. Personally I have a ton of OP07 (good precision low offset opamp), some NE5532 for audio stuff, some old 741ish and 358 for generic use, a couple of expensive op177 andsome DIP tubes of LM3902 quad opamp (general purpose again) and LM339 comparators.Again, this fits my general prototyping needs

author: Unixon
author_rank: Frequent Contributor
timestamp: August 09, 2020, 09:40:36 pm
content: Well, op amp selection heavily depends on the problem you're solving, there's no general advice on particular parts.However, I can name a few that eventually were found to be a good choice and later got wider use in projects.Few notes about mentioned op amps:LM358/LM3902 and alike - cheap and popular but you should watch out for biases or they may come after you when you least expect it.LM386/NE5532 - special cases for audio, never tried to use them for any other jobs.Some of my findings:LMV321/LMV358/LMV324 - kind of rail-to-rail op amps, low voltage, slightly better than non-R2R LM* counterparts;TSV524IQ4T/TSX564IQ4T - tiny QFN 4-channel R2R bastards, if you need to save board space;TL061,TL081 and alike - JFET inputs, next option when bipolar are too leaky;TLV237x - good R2R parts (x=1,2,4) - small biases and wide operating range;TSX561 - good replacement for LMV321;MCP600x - cheap and good R2R parts (x=1,2,4) somewhat similar to TLV237x - check operating range and other parameters;AD859x - tiny, high output current, but no protection, good for driving fixed load;CA3140 - special part for very low input leakage;LTC6915 - cool programmable amplifier (PGA);Always compare part's characteristics to your requirements.

author: David Hess
author_rank: Super Contributor
timestamp: August 09, 2020, 11:47:14 pm
content: Keep things simple by sticking with single and dual parts which are easier to use than quads.OP-07 - Low cost precision.LM358 - Low cost single supply general purpose, half of an LM324.TL071 or TL081 - Low cost single JFET input.TL072 or TL082 - Low cost dual JFET input.TL074 or TL084 - Low cost quad JFET input.LM301A - Externally compensated 741 replacement which can also be used for high side applications.

author: zrlopez
author_rank: Contributor
timestamp: August 12, 2020, 04:47:10 pm
content: @Unixon: Ya, I guess I was looking for some good common, general use op amps to have like the 741 and 358 @ceoxrad mentioned. I watched a couple of Jones' EEV blog videos comparing op amps, but with so many options to consider, it can feel like a bit much. As a beginner, building a basic AM/FM radio circuit should I prioritize leakiness, biases and save wide operating range requirements for future models of my design haha.

author: zrlopez
author_rank: Contributor
timestamp: August 12, 2020, 04:50:32 pm
content: Is the LM358 the main general purpose op amp you prefer, or are there a few other generals that you like. Again I know they're not perfect with biases and leakiness, but I want a couple general ones to compare to

author: ceoxrad
author_rank: Regular Contributor
timestamp: August 12, 2020, 05:23:16 pm
content: Yes the LM358 is a pretty common and cheap general purpose part.It's performance is marginal to say the least (the only thing it does good is working with a single rail near ground...) and there are much better designs out there for pretty cheap.Sometimes you need a simple buffer and here you have an application for it,but you have to know well it's limitations, personally I use it quite sparsely these days. I have inherited a ton of OP07 from a previous job and just use those usually.

author: magic
author_rank: Super Contributor
timestamp: August 12, 2020, 07:39:31 pm
content: RC4558/RC4559/RC4560 are dirt cheap, about on par with µA741 (or faster) and two in one package.They don't work at the negative rail and I believe they have "phase reversal" there, like TL072.

author: Zero999
author_rank: Super Contributor
timestamp: August 12, 2020, 09:04:41 pm
content: Quote from: zrlopez on August 12, 2020, 04:50:32 pmThe LM358 & LM324 are really only good for DC. They have horrible crossover distortion, which means its output stage needs to be biased, with a resistor, so the current through the output stage doesn't change direction.

author: Unixon
author_rank: Frequent Contributor
timestamp: August 12, 2020, 10:00:51 pm
content: Quote from: zrlopez on August 12, 2020, 04:47:10 pmGot it, in short: I would drop LM358 for R2RIO TLV2372 (or R2RO TLV272) and LMV358 for R2RIO MCP6002.

author: james_s
author_rank: Super Contributor
timestamp: August 12, 2020, 10:11:08 pm
content: The LM386 isn't an op-amp, it's an audio power amplifier. Conceptually it is similar but it is designed for a specific purpose.My usual go-to for prototyping and general purpose stuff is the TL081/TL082, they are inexpensive, readily available and offer reasonably good performance.

author: Unixon
author_rank: Frequent Contributor
timestamp: August 12, 2020, 10:36:05 pm
content: Q: Isn't 741 a mammoth age design? Should we be using it anywhere these days?

author: David Hess
author_rank: Super Contributor
timestamp: August 12, 2020, 11:25:11 pm
content: Quote from: Zero999 on August 12, 2020, 09:04:41 pmFor most applications the crossover distortion of the 358/324 is not important. And even in audio applications, it usually does not matter except at low signal levels. If it does, then add a shunt output resistor or current source to force class-A mode. Audio applications usually benefit from a completely different part anyway.A not too expensive direct high performance replacement for the single supply dual/quad 358/324 are the LT1013/LT1014 which also come in the LT1006 single version which supports offset null. These are precision parts with low offset and also have class-AB output stages. if you squint a little bit, the LT1006 might be considered a single supply version of the precision OP-07.There are higher performance operational amplifiers now which are more "universal", but they cost more:LT1008/LT1012/LT1097 - Precision low input bias current - Improved 308 - More general purpose "precision" than OP-07.LT1006/LT1013/LT1014 - Single/Dual/Quad precision improved performance single supply 358/324 replacement.There are also rail-to-rail output versions of the above now but there will never be equivalent rail-to-rail input versions. Still, there are some pretty good rail-to-rail input and output parts if you can accept compromised performance. I try to avoid them because they are mostly useful where supply voltage selection is limited.Quote from: Unixon on August 12, 2020, 10:36:05 pmYes, people should be using the 301A instead.Newer low cost parts are not generally any better than the 741, and many are worse, so there is no reason not to use it, or the 301A which has some advantages, where appropriate. If you can accept a cost premium, then there are lots of parts better than the 741 like the LT1008/LT1012/LT1097 which outclass it in every way except differential input voltage range.

author: james_s
author_rank: Super Contributor
timestamp: August 13, 2020, 04:30:41 pm
content: Quote from: Unixon on August 12, 2020, 10:36:05 pmIt's an ancient part but if you have some laying around there's no reason not to use them for applications for which they are suitable.

author: David Hess
author_rank: Super Contributor
timestamp: August 14, 2020, 12:51:01 am
content: Quote from: james_s on August 13, 2020, 04:30:41 pmThe only reason the 741 is not suitable for new designs is that it *should* cost more because it does not use transconductance reduction which reduces the size of the expensive compensation capacitor. Its modern replacements like the dual RC1458 combine the 741 topology with transconductance reduction and they are very inexpensive.There are also PNP input replacements for the 741 like the quad RC4136 and dual RC4558/RC4559/RC4560 that magic mentioned. I suspect they use transconductance reduction but unlike the RC1458, I have not seen any schematics which show it; usually it is left out of the simplified schematic.