Equivalent to CA3240 - Page 1
Forum section: electronics / beginners

author: aless2056
author_rank: Contributor
timestamp: August 05, 2022, 01:55:47 am
content: Hello guys, my friend needs the CI CA3240, but this item is missing from distributors (Farnell, Mouser, Digikey,...).What would be the option to replace this CI in DPID format?

author: wizard69
author_rank: Super Contributor
timestamp: August 05, 2022, 02:08:36 am
content: rght on the first page of the datasheet: "The CA3240A and CA3240 are compatible with the industrystandard 1458 operational amplifiers in similar packages.".

author: edavid
author_rank: Super Contributor
timestamp: August 05, 2022, 02:18:36 am
content: Quote from: wizard69 on August 05, 2022, 02:08:36 amYeah, that's totally unhelpful. The CA3240 has the same pinout as the 1458 (and every other dual op amp), but otherwise it's not at all similar.OP, I'd suggest making a carrier board with 2 CA3140s in SO8, since that's still in production, although wildly overpriced.Otherwise you'll have to analyze your circuit to see what kind of CMOS or JFET dual op amp will work. Could be as simple as a TLC272 or LF356, could require something exotic.

author: Kleinstein
author_rank: Super Contributor
timestamp: August 05, 2022, 04:43:27 am
content: AFAIK there is no easy direct replacement with a common chip. If the circuit is known one has more freedom, knowing which parameters are important. The TLC272 may work if the supply voltage is below 16 V.However man modern OP-amps are not available in DIP. Otherwise an OPA2991 or TLV9352 would be a good bet.

author: Zenith
author_rank: Frequent Contributor
timestamp: August 05, 2022, 07:10:03 am
content: Quote from: aless2056 on August 05, 2022, 01:55:47 amIs he obliged to buy it from Farnell etc? A quick look shows there are many sellers of this chip in DIP form; ebay, smaller sellers etc.

author: wraper
author_rank: Unknown
timestamp: August 05, 2022, 07:21:04 am
content: I would buy an opamp from Ali or ebay only if totally desperate as most of opamps sold there are fake. 10 pieces for $2.50 are guaranteed to be such. Utsource is much better but still quite high possibility of fakes so verifying what you got is a must.https://www.utsource.net/itm/p/11535112.html

author: Zenith
author_rank: Frequent Contributor
timestamp: August 05, 2022, 07:31:32 am
content: ebay is a lottery, however there are reputable sellers who've been selling to hobbyists for years, and specialists in obsolete components who carry NOS. Some of them sell on ebay. utsource looks good. Even Farnell have been caught out with fakes occasionally.I don't know how accessible these sources are in Brazil, but it seems like an easier route than finding an equivalent.

author: wraper
author_rank: Unknown
timestamp: August 05, 2022, 07:45:02 am
content: Quote from: Zenith on August 05, 2022, 07:31:32 amNot aware of such cases, however there were some issues on manufacturer side. Like FTDI screwing up with serial numbers and their driver detecting genuine FT232 IC as fake, or a batch of MAX31855K thermocouple-to-digital converter with wrong calibration due to screw up by the factory.

author: Zero999
author_rank: Super Contributor
timestamp: August 05, 2022, 09:21:00 pm
content: You won't get through hole. The TLV2172 appears to be a good candidate, but it'll need to go on an adaptor board, if your PCB is through hole and you can't remake it.https://www.ti.com/lit/ds/symlink/tlv172.pdf

author: rooppoorali
author_rank: Regular Contributor
timestamp: August 07, 2022, 12:34:11 pm
content: This article says that the CA3240 is equivalent to TTL based LM741 IC and can replace one another in many applications.https://microcontrollerslab.com/ca3240-bimos-op-amp-with-mosfet-input-bipolar-output/

author: Zero999
author_rank: Super Contributor
timestamp: August 07, 2022, 01:30:48 pm
content: Quote from: rooppoorali on August 07, 2022, 12:34:11 pmThat's not true at all. The CA3240 can't just be blindly replaced by the 741. It's a dual op-amp IC, whilst the 741 is single. It also has a much wider bandwidth, slew rate, higher input impedance and lower bias currents, than the 741.

author: Zenith
author_rank: Frequent Contributor
timestamp: August 08, 2022, 11:38:47 am
content: Quote from: rooppoorali on August 07, 2022, 12:34:11 pmDepending on the details of the OP's circuit it might be possible to replace it with virtually any dual op amp. The CA3240 may have been selected because they had a lot of them on hand. On the other hand the CA3240 may have been carefully chosen for its particular properties, such as extremely high input impedance.Especially if the chip had to be soldered in place, I wouldn't just bung in a 1458 (dual 741) and hope for the best.

author: CaptDon
author_rank: Super Contributor
timestamp: August 08, 2022, 11:58:09 am
content: Maybe the O.P. could give some details of the circuit surrounding that CA3240? Unless it is some kind of mega high impedance circuit used with instrumentation or capacitive sensor. If it is a more conventional circuit then there are many choices. I have used some 8 pin dual opamps from A.D. that have GBP up to 20Mhz. I have seen the 3240 used in simple audio circuitry and there are so many better choices available today.

author: Zenith
author_rank: Frequent Contributor
timestamp: August 08, 2022, 02:56:22 pm
content: We also don't know how many are required.Is this a piece of equipment being repaired so one will do? In that case, it's not that hard to find a NOS 3240. It may cost a lot, say $10, but considering the cost and trouble of messing about with a plug in replacement board with SMDs, it might be considered cheap. The Buy/Sell/Wanted section on this forum may produce results.Is this a production run of some obsolete unit for which there's seen to be a demand, so there's an initial requirement of 500? In that case there are specialist sellers of obsolete chips who don't deal in small quantities, or the replacement board approach makes sense.