SOIC8 Dual Opamp "003" With Odd Pinout - Page 1
Forum section: electronics / repair

author: David_AVD
author_rank: Super Contributor
timestamp: October 24, 2019, 01:31:57 am
content: Has anyone seen dual opamps with a non standard pinout?The ones in question are marked 003 and are a SOIC8 package.Pin 2 seems to be V- (0V) and pin 6 is V+ and I've not come across that before.There are in a Digitech powered speaker and of course there is no data available.

author: Kleinstein
author_rank: Super Contributor
timestamp: October 24, 2019, 06:21:08 am
content: The LT1013 is know for it's odd pinout in SOIC8. However I very much doubt this is the OP used in an audio application. In the old days there where a few OPs with different pinout, but this was mainly before SOIC8.It this actually an OP, or is it a kind of power amplifier ?

author: David_AVD
author_rank: Super Contributor
timestamp: October 24, 2019, 06:40:42 am
content: There are several of these 003 chips in the preamp section of the powered speaker, so they will be opamps. The surrounding components are arranged for feedback, etc.I don't know why someone would even come up with a non-standard pinout of such a common item in the first place.EDIT: The LT1013 does seem to be correct with respect to the power pins.

author: magic
author_rank: Super Contributor
timestamp: October 24, 2019, 06:59:01 am
content: Is this what it looks like? Maybe your chips are simply LT1013. Maybe there are others with this pinout.Notice that the pinout is identical to DIP8, but shifted clockwise by two pins. I suspect it's because the die has unusual dimensions, wide and short, too wide to fit into SOIC package, so they rotated it by 90° and modifed pinout to match the new orientation.editActually, it's not even unusual for dual opamps to be laid out that way. Here's one common example:ST TL072. The central axis pads are power, and the sides are bottom-up: IN+, IN-, OUT.You can see how it correlates with external pinout and you can imagine what happens if the die is too wide to go into SOIC (the TL072 is not) and has to be rotated.

author: David_AVD
author_rank: Super Contributor
timestamp: October 24, 2019, 07:09:49 am
content: I've just had another look at the PCB and the pinout does seem to make sense for an LT1013 or similar device. It also confirms that one opamp out is slammed to the V+ rail so that is likely a faulty chip. Thanks guys.

author: magic
author_rank: Super Contributor
timestamp: October 24, 2019, 07:26:12 am
content: If the chips are only marked 003 then it probably is not LT1013, unless LT's factory markings have been scratched off and painted over.

author: David_AVD
author_rank: Super Contributor
timestamp: October 24, 2019, 09:24:05 am
content: I'm not aware of any way to search devices with a specific pinout, so the LT1013 is my only choice right now.

author: picburner
author_rank: Frequent Contributor
timestamp: October 24, 2019, 03:04:03 pm
content: LT1124 also has the same power supply pinout.It is also a dual low noise op-amp.

author: David_AVD
author_rank: Super Contributor
timestamp: October 24, 2019, 08:09:33 pm
content: The LT1124 appears to be a very expensive chip. The item being repaired is a cheap powered speaker with 4 or 5 of the 003 chips, so they will be some sort of lower spec dual opamp. I might be able to wire a DIP package onto the PCB as a test.

author: magic
author_rank: Super Contributor
timestamp: October 24, 2019, 09:16:31 pm
content: LT1013 or LM358 is marginal for audio, rather slow. But it will work, somewhat.How old is that thing, are there any other, "branded" chips in there? Maybe that could offer some clue as to what the original 003 chip might be.

author: David_AVD
author_rank: Super Contributor
timestamp: October 24, 2019, 09:31:21 pm
content: It's only a couple of years old and still a currently sold product. The 003 chips are the only ones on the preamp / mixer boards. The rest of the amp is a switchmode PSU and class D amp with passive crossover.

author: David_AVD
author_rank: Super Contributor
timestamp: October 30, 2019, 10:01:12 am
content: LT1013 installed, speaker now working, job out the door. Thanks again.