BJT Matched Pair - Page 1
Forum section: electronics / beginners

author: MAntunes
author_rank: Regular Contributor
timestamp: January 02, 2016, 04:47:42 pm
content: Hello, does anyone know where to find a BJT Matched Pair IC in a DIP package and with a reasonable price?All I can find is small SMD packages or very strange DIPs with very high prices. I wanted a breadboardable IC.I want a NPN pair, for PNP Analog Devices makes the SSM2220.Thank you for your help!

author: cvanc
author_rank: Frequent Contributor
timestamp: January 02, 2016, 05:03:09 pm
content: The LM394 'supermatch pair' is obsolete but maybe you can find some? It came in a DIP and a round can, as I recall...http://www.ti.com/lit/ds/symlink/lm194.pdf

author: Kleinstein
author_rank: Super Contributor
timestamp: January 02, 2016, 05:04:13 pm
content: Matched transistors are not vry comon any more. So they are generally relatively expensive and a little hard to get. In many cases they are replaced by higher integrated chips like OPs.So for lower qualitiy you may just glue two matched 2N3904/6 together.Sometimes on can use chips with slightly more transistors, like the CA3054 - which is long tailed pair with a current source at the emitters.

author: dom0
author_rank: Super Contributor
timestamp: January 02, 2016, 05:41:30 pm
content: The CA3046 is still available NOS, too.I'd just recommend matching transistors yourself, or buying transistor on rail. I noticed that nearby transistors on a rail tend to be matched fairly well, at least for these I actually have on rail (BC548, BC547 and 337/327, all Philips NOS).

author: alsetalokin4017
author_rank: Super Contributor
timestamp: January 02, 2016, 05:45:21 pm
content: Lots of Ebay sellers of LM394, in can and 8pin DIP.Looks like they run from about 3 to 5 dollars US each. Cheaper in quantity.

author: Vgkid
author_rank: Super Contributor
timestamp: January 02, 2016, 05:51:30 pm
content: The dip package is rather uncommon, are you willing to use a TO-71/78 package?This might be of help.http://www.linearsystems.com/products.php?pr=transistorsyou can buy them here:https://www.trendsetter.com/Transistors-s/23000.htm?searching=Y&sort=11&cat=23000&show=20&page=1&f-NPN=23302ELSE remove the LS, and determine the other entry digits and search on ebay, use their model x-reference lookup tableselection guidehttp://www.linearsystems.com/literature_sub.php?p_id=7silliconix/fairchild cross refhttp://www.linearsystems.com/literature_sub.php?p_id=8

author: Zero999
author_rank: Super Contributor
timestamp: January 02, 2016, 06:03:20 pm
content: What is it for?There isn't much need for discrete matched transistors nowadays as IC op-amps have made them obsolete.If it's for experimenting with then you could buy a large quantity of transistors and sort them by Hfe, as mentioned above. The problem then is the transistors still need to be at exactly the same temperature, so they remain matched. To achieve this, place the transistors next to one another and bend the legs so the packages physically touch one another.Another thing you could do, is get a SMT matched transistor IC and mount it on a DIP break out board.

author: MAntunes
author_rank: Regular Contributor
timestamp: January 02, 2016, 07:35:05 pm
content: Thank you all for the help.It's for an exponential current source like this one:I would like for the transistors to be matched so I started searching for ICs.

author: dom0
author_rank: Super Contributor
timestamp: January 02, 2016, 07:43:53 pm
content: Ah, yeah, the thing about translinear circuits is, that they need really well matched transistors or they all drift like hell and have huge offsets. Even with good matching of Ube and dUbe/dT they tend to still drift a lot and be inaccurate in general.To me it the TLP always seemed at home in integrated circuits, not really in discrete designs...Just my two cents on the topic. Maybe I just didn't try hard enough?

author: MAntunes
author_rank: Regular Contributor
timestamp: January 02, 2016, 11:45:26 pm
content: I actually found a company that makes Matched Pair in DIP package, THAT Corporation.http://www.thatcorp.com/300-series_Matched_Transistor_Array_ICs.shtmlBut they are a bit expensive 6.25€+VAT for the 2 NPN and 2 PNP. I emailed them to see if they can supply me some samples, I was worth a try.Another thing, are there any kind of single BJT that are more prone to be matched than the 2N3904/6 or similar?Best regards,Miguel Antunes

author: Lee Leduc
author_rank: Regular Contributor
timestamp: January 03, 2016, 01:30:58 am
content: Music From Outer Space is a site about analog synthesizers. Ray Wilson has an article entitled "Transistor Matching 101" about transistor matching for exponential converters used in VCO's.The web page ishttp://www.musicfromouterspace.com/index.php?MAINTAB=HOME&VPW=1024&VPH=790.Look for the article under the "SYNTH-DIY" tab on the home page. Using a batch of 100 2N3904's and 2N3906's I've used the info in his article and came up with about 2 dozen PNP and NPN matched pairs good enough for a 5 octave VCO. Check it out, it may meet your needs .

author: reimius
author_rank: Newbie
timestamp: May 19, 2021, 03:11:27 pm
content: Maybe useless reply since this a quite old inactive thread, but I found this at Mouser:MPQ2222:https://eu.mouser.com/ProductDetail/Central-Semiconductor/MPQ2222A-PBFREE?qs=l7cgNqFNU1hcO2ukcAJBdw%3D%3D300P14-U:https://eu.mouser.com/ProductDetail/THAT/300P14-U?qs=9Udfh7QmL4vaHxAiVJNK9A%3D%3DBoth Quad matched NPSs.I hope that could help someone

author: TimFox
author_rank: Super Contributor
timestamp: May 19, 2021, 03:21:27 pm
content: The MPQ2222 is four independent 2N2222-type transistors mounted in a DIP package, but they are not matched. This format was popular around 1980 to mount general-purpose transistors in circuit boards designed for DIP packages.

author: reimius
author_rank: Newbie
timestamp: May 19, 2021, 03:28:29 pm
content: Sorry then, I though that when they are at the same die they should be matched! Thanks for pointing out my mistake

author: edavid
author_rank: Super Contributor
timestamp: May 19, 2021, 05:12:11 pm
content: Quote from: reimius on May 19, 2021, 03:28:29 pmThey are not on the same die, just in the same package. You can tell this is the case since there is no substrate pin like on the CA3046.Quote from: Lee Leduc on January 03, 2016, 01:30:58 amMore current link:http://musicfromouterspace.com/index.php?MAINTAB=SYNTHDIY&PROJARG=TRANSISTORMATCHER/TRANSISTORMATCHER.html&VPW=1427&VPH=876

author: ledtester
author_rank: Super Contributor
timestamp: May 19, 2021, 05:26:51 pm
content: QuoteYou can get SMD breakout boards for cheap -- search aliexpress/ebay for "smd adapter", e.g.:https://www.aliexpress.com/item/1005002364822427.html

author: Zero999
author_rank: Super Contributor
timestamp: May 19, 2021, 06:12:49 pm
content: I've recently discovered Diodes Inc. make matched BJT pairs. They're properly matched and reasonably priced, compared to other vendors.DMMT5551NPNDMMT5401PNP

author: Benta
author_rank: Super Contributor
timestamp: May 19, 2021, 07:27:13 pm
content: Quote from: Zero999 on May 19, 2021, 06:12:49 pmEven better are the parts from Linear Systems (a company producing otherwise obsolete parts).As an example, the LS318 on this page:https://www.linearsystems.com/product.html?category=Bipolars

author: Zero999
author_rank: Super Contributor
timestamp: May 19, 2021, 08:45:06 pm
content: Quote from: Benta on May 19, 2021, 07:27:13 pmI'm sure they're better, but I bet they cost a darn sight more.

author: Benta
author_rank: Super Contributor
timestamp: May 19, 2021, 10:27:46 pm
content: You're probably right. I have no idea on pricing.Still, it's nice that such parts are available.

author: TimFox
author_rank: Super Contributor
timestamp: May 20, 2021, 01:57:19 am
content: Note that the LS data sheets explicitly state the matching criteria: difference between Vbe and Ib under stated conditions of Vce and Ic.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: May 20, 2021, 05:25:37 am
content: Note that the matched-die kind are susceptible to thermal runaway like in current mirrors, or exhibit substantial drift in diff amps, etc. Substantial for a precision application I mean, the kind of thing Tektronix went to great lengths to deal with back in the day.Tim

author: Kleinstein
author_rank: Super Contributor
timestamp: May 21, 2021, 06:36:36 pm
content: If reasonable close in the same case and limited power level, the coupling can be good enough even with seprate dies. For current mirrors additional emitter resistors can improve things quite a bit - up to the point of no longer needing matched pairs.

author: blackdog
author_rank: Frequent Contributor
timestamp: May 21, 2021, 07:19:31 pm
content: Hi,Analog Devices,SSM2210andSSM2212Are still for sale.https://www.analog.com/en/products/ssm2212.html#product-overviewKind regards,Bram

author: David Hess
author_rank: Super Contributor
timestamp: May 23, 2021, 05:09:56 am
content: I think the forum restores erased my comment.THAT Corporationsells matched monolithic quads but they are not cheap.Quote from: T3sl4co1l on May 20, 2021, 05:25:37 amThe problem is that if the collector voltage is constant, then driving the differential pair causes one transistor to dissipate more power and the other to dissipate less. The solution Tektronix used is to add a bypassed resistor between each collector and the following cascode transistor to halve the collector voltage. Now when the differential signal moves away from zero, the voltage rises and current decreases on one transistor, while the voltage decreases and the current rises on the other, making the power dissipation of each transistor relatively constant, and matched between them.