Opamp chip identification - Page 1
Forum section: electronics / beginners

author: johnny911
author_rank: Newbie
timestamp: January 19, 2022, 01:52:34 am
content: Hi, pals!I'm in process of restoring piece of old junk. And I was failed to identify one of the operational amplifiers.Does anyone have idea what kind of animal this is?

author: rpiloverbd
author_rank: Regular Contributor
timestamp: January 19, 2022, 08:29:08 am
content: The closest option that comes in my mind is LM318.https://datasheetspdf.com/pdf/1136708/NationalSemiconductor/LM318/1If possible, Kindly check with a multimeter if your IC has GND in pin#4 and VCC in pin#7.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 19, 2022, 09:03:28 am
content: A LM318 is a candidate, though I have not see such a crude marking for such a part.The soldering at the chip look rather poor - so maybe give it a try and resolder the pins.What type of gear is this ? This can give a hint what properties for the OP are needed and thus limit the possible candidates.

author: magic
author_rank: Super Contributor
timestamp: January 19, 2022, 12:01:25 pm
content: How important is it to recognize it? If you are repairing something here, do you have a schematic of the surrounding circuit?LM318 pinout is the same as 99% if not 100% of DIP8 single channel opamps. Differences may exist on pins 1,5,8 → see point above.Do you recognize the logo on this IC, does it appear on other chips in the same device? The "318" in LM318 would typically be preceded by letters "LM" or maybe other letters specific to an alternative manufacturer. A number consisting of all digits may be a proprietary part number of the manufacturer of this device.

author: johnny911
author_rank: Newbie
timestamp: January 19, 2022, 01:34:44 pm
content: Quote from: rpiloverbd on January 19, 2022, 08:29:08 ampin#3 GND, pin#4 -12V, pin#7 +12VQuote from: Kleinstein on January 19, 2022, 09:03:28 amGood shot. But I am confused by the presence on the board of lm318 with normal markings. Accordingly, if it is lm318, then it should be somewhat special. Moreover, I have a second exactly the same board and the situation is the same with the chips: two normal lm318 and one with the same orange marking.Quote from: Kleinstein on January 19, 2022, 09:03:28 amOne board is completely dead, other is noisy. For now, I'm documenting schematic and identifying unknown components. I haven't started the repair yet.Quote from: Kleinstein on January 19, 2022, 09:03:28 amThis is amplifier board from gamma spectrometry multichannel analyzer.Quote from: magic on January 19, 2022, 12:01:25 pmOf course, if the chip has to be changed, I will start with lm318. But if possible, I would like to find out the manufacturer and the exact chip model so that after the repair the device does not worsen its characteristics. After documenting the schematic, I will add a schematic fragment with this chip to the topic.Quote from: magic on January 19, 2022, 12:01:25 pmUnfortunately the logo is not familiar to me. An orange marking with this logo is present on the single chip on the board. On the second same board, on the same chip, the marking looks exactly the same, but in worse quality. I'm pretty sure the device manufacturer didn't make chips, so it must be something standard.

author: magic
author_rank: Super Contributor
timestamp: January 19, 2022, 01:54:09 pm
content: The manufacturer could have internal part numbers for standard chips (or maybe customized/selected grades of otherwise standard chip) and order parts with the custom numbers printed on them.But if other chips have normal markings and the logo is not of the manufacturer and not of any well know semiconductor vendor, then

author: Kleinstein
author_rank: Super Contributor
timestamp: January 19, 2022, 02:27:59 pm
content: If there are normal LM318 already in the circuit, it is somewhat unlikely this is a LM318 too.So maybe draw a schematics for the circuit around this chip and than find a suitable modern OP for that task. This may not be the same chip, but well possible to find a better one - though the need for DIP could limit the choice.

author: jwet
author_rank: Frequent Contributor
timestamp: January 19, 2022, 03:14:54 pm
content: I think the 0318 is a date code and its a house numbered (proprietary) part. Judging by the tantalums surrounding it, my guess would be an ICL7660 or equiv. This are inverting charge pumps that can take 5V and make -5v at low currents. Precision and high speed circuits often use these to do "single supply" with good op-amps. R-R input op-amps usually have a funny input structure (P and N) that degrade precision. See if that makes sense and if it makes negative volts.

author: golden_labels
author_rank: Super Contributor
timestamp: January 19, 2022, 03:25:57 pm
content: If that helps, multiple sources identify the AS logo as Analog Systems.(1)(2)(3)(4)Unfortunately I can’t quickly find information on them: being a common phrase, “analog systems” is not exactly making to the top of the results. Weak links include aWikiBooks entryan anonymous user has once added (listed with Marconi Company) and FinnishMicro Analog Systems, but that’s a poor match — in particular with no fitting logos.I doubt it’s an op-amp, thought. Assuming there is no SMD resistors on the other side, I can only see capacitors in the direct vincinity of the chip. That would be an unusual configuration for an op-amp.(1)Diverse Devices,logo #20in upper left corner,the associated description.(2)Dial Electronics(archived)(3)Canics, A-L, row 7, column 3(archived)(4)IC-Logos(archived)

author: johnny911
author_rank: Newbie
timestamp: January 20, 2022, 01:36:38 pm
content: Thank you all for the helpful hints and ideas.Finally, I documented the section of the circuit with 00318 chip.This is definitely a charge sensitive preamplifier. I found on this forum the topic "Charge sensitive amplifier for photomultiplier" with a discussion related to CSPs and opamp recommendations.What do you think, Can the OPA141 be installed in place of 00318, with SO-8 to DIP-8 adapter? Or is there an opamp with characteristics similar to OPA141 in DIP-8 package exists?And for the history, I attached a photo of the complete amp pcb. It's part of the ND-SIX MCA.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 20, 2022, 02:43:24 pm
content: The OPA134 is relatively similar to the OPA141 and available in DIP. It is slightly higher noise and higher offset, but still a relatively good JFET OP. The OPA627 would also be possible, but a bit on the expensive side.A charge sensitive amplier would make sense with FET OP.

author: magic
author_rank: Super Contributor
timestamp: January 20, 2022, 02:59:25 pm
content: Quote from: golden_labels on January 19, 2022, 03:25:57 pmSeems right but it must be a fairly obscure company.Linear had some JFET opamps in DIP but pricey. Do you care about offset voltage? If not, OPA1641 is similar to OPA141 but not trimmed for DC specs so cheaper. And still SMD only.It's a good idea to check for anything connected to the nonstandard pins (1,5,8) that could play tricks on you.

author: johnny911
author_rank: Newbie
timestamp: January 21, 2022, 06:29:59 pm
content: Quote from: magic on January 20, 2022, 02:59:25 pmIf I understand offset voltage phenomenon correctly, this will add a small DC offset to the op-amp ouptput. In the case of an MCA that performs relative voltage measurements, the op-amp offset voltage, probably, has little or no effect on the result. Anyway, I prefer the DIP package option.Quote from: magic on January 20, 2022, 02:59:25 pmThe attached schematic fragment is complete, except for the missing decouplig caps. 1,5,8 pins are not connected at all.Quote from: Kleinstein on January 20, 2022, 02:43:24 pmThank you. It seems that the OPA134 op-amp is way to go.

author: magic
author_rank: Super Contributor
timestamp: January 21, 2022, 08:20:42 pm
content: Sorry, I missed your schematic.Offset voltage means that it will not try to make IN- exactly equal to IN+ (ground), but a few mV more or less.So you are correct about the output. Also, the detector will be biased to ± few mV rather than zero exactly, whatever the opamp's spec is.

author: johnny911
author_rank: Newbie
timestamp: January 21, 2022, 09:58:43 pm
content: Thank you for explanation.

author: magic
author_rank: Super Contributor
timestamp: January 23, 2022, 12:59:34 am
content: Analog Systems, Tucson, Arizona. I have heard of them beforehttps://www.diyaudio.com/community/threads/the-ne5534-misunderstood.29360/page-4I even have that MA332 datasheet.https://www.alldatasheet.com/datasheet-pdf/pdf/130007/ETC1/MA332.htmlBTW, they say that MA332 was rebranded RC5534 selected for THD, but I see a small problem:- MA332 was unity gain stable with 3nF load; 5534 are unity gain stable IME with resistive load but I'm not sure if they take 3nF- pin 5 is described as NC but 5534 has compensation thereIt may still be true in the sense that it was a customized RC5534 they ordered from Raytheon, or maybe the DS was not accurate or maybe ordinary 5534 also meet those specs.Anyway, if it's true that AS simply sold selected or customized chips of other manufacturers then you won't easily identify your chip. I can't find any databook of those guys, only two individual datasheets so far. The part number doesn't make sense and doesn't resemble those I know (MA-xxx), so it may have been a custom order from the manufacturer of your board, perhaps.There is always one way, though, which may at least offer some cluehttps://www.eevblog.com/forum/projects/decapping-and-chip-documentation-howto/(If you feel like sending the chip to Germany, contact the author of that post).

author: johnny911
author_rank: Newbie
timestamp: January 23, 2022, 02:53:38 pm
content: Wow, excellent research! To be honest, I was sure that the manufacturer's logo was placed rotated by 90 degrees, and the last letter is "D". As it turned out, it is placed vertically and exactly matches the logo from the datasheets.With the latest information, I was able to find a reference book of linear discontinued components atBitsaver. And it mentions the MA00318CP op-amp from Analog Systems. The databook even lists some of the electrical parameters of the MA00318CP.So it is very likely that the mystery is finally solved.Sending chip for decapping is too much as for me :-)

author: magic
author_rank: Super Contributor
timestamp: January 23, 2022, 04:34:58 pm
content: Nice bookThe specs are not spectacular, it looks like TL071 could have a chance.

author: Kleinstein
author_rank: Super Contributor
timestamp: January 23, 2022, 04:43:49 pm
content: Quote from: johnny911 on January 23, 2022, 02:53:38 pmThat is an very insteresting data-book.The data for the MA00318 look like nothing special at all - more like close to a 741. So rather low speed and quite some input bias (BJT based).

author: magic
author_rank: Super Contributor
timestamp: January 23, 2022, 04:51:54 pm
content: 100nA Ib is wort case and 741 barely qualifies "typically" at 25°C. I thought about OP07, but its dynamic performance is nothing to write home about and it's not clear what slew rate is required.I can't find the 7LM41HX drawing which is supposed to show this part.7LM40HX shows something like TL072, 7LM41LX shows 741 with JFET input buffers.