Need Help Finding Alternatives for BD140-10 and BD139 Transistors

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tavares_costa

tavares_costa

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Joined 2023
#1
Hi DIYAudio community,

I'm currently working on a DIY audio amplifier project, and I've run into a bit of a roadblock. The transistors I planned to use, specifically the BD140 (PNP) and BD139 (NPN), are unfortunately out of stock and unavailable from my usual suppliers.

I'm reaching out to the knowledgeable members of this community to ask for assistance in finding suitable alternative transistors that can perform the same function as drivers in my circuit. The BD140-10 and BD139 are critical components for the project, and I want to make sure I choose replacements that will work seamlessly.

If anyone has experience with this situation or has worked with alternative transistors in similar applications, I would greatly appreciate your recommendations and insights
 
#2
I have used On Semi MJ15028/29 as drivers of output transistors in class AB power amplifiers. They have a bigger footprint than BD139/140 but with a heatsink attached, have never blown. They are BCE pinout. Do not accept MJE15030/31 MJE15032/33, MJE15034/35, those have higher capacitance.
I used them in a circuit that suggested 2sa1837 2sc4397 but in USA these toshiba numbers I have never seen stocked by any authorized distributor. In Europe people seem to buy Toshiba parts all the time.
These replaced TO5 packages 2n5320/5322 in my amp which were EBC. At times these have been stocked from Thompson and later ST. I have a couple of surviving RCA ones from 1970, produce sparkling highs on single pair MJ15003 output transistors.
 
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#3
Digikey did carry the A1837/C4793 - about 15 years ago. I bought them before they disappeared. The new TTA006/C011 are the SAME THING in a TO-126, which matches the BDs. A better match to the BDs are the TTA004/C004 which are lower voltage and tend to have higher gain. If the OP has problems getting BD139/40, though, I imagine getting real Toshibas will be even harder. Fakes everywhere.
 
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#7
Won’t (or shouldn’t) be above +/-40V if the BDs were being considered. Wouldn’t need 120,160 or 230V transistors, but in most cases it won’t hurt anything either. Those higher voltage alternatives are usually more expensive than the generic BD139/40. And unfortunately, more likely to be fakes if you have to buy them on the gray market. So watch it.

Mouser is not necessarily available everywhere in the universe. In the free world, with a credit card, yes. But that’s not universal.
 
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#8
tavares_costa said:
I'm planning the design using SC5200/1943 on the output stage, will the MJ15028/29 fit well?
Click to expand...
On Semi MJE15028/29 have a 40 v soa of about .8A so they are suitable mostly as drivers. 30 mhz Ft makes for sparkling highs. As compared to TIP31c/32c (6 mhz) which sounded like sludge on the highs. Too obscure to be faked IMHO.
2SA1943 has soa @ 40 v of ~3A, 2sc5200 about 4 A. Have good gain at 7 A. Good output transistors in 50-70 w amps. However, you probably won't be buying genuine Toshiba, probably some sort of oriental clones. A number pretty heavily faked.
 
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#14
MJE340/50 are getting even further away. Even higher voltage, even less gain (sub-100). More suited to VAS and predriver duty in BIG amps. If you want old-school MJEs, use MJE243/253 if you're at 80V supply. They are the device of choice in the old Naim clones. But everyone uses the 1502x now, useable in amps from 20W to 200, depending on voltage grade. Plenty enough SOA. You just don’t have to think about it, other than getting a high enough voltage version.
davidsrsb said:
There's no frequency information in the ST and Onsemi datasheets
The SOA of a BD139 is poor, 200 mA at 40V and just 60mA at 80V (dc)
Click to expand...
You will never find a driver type transistor that can handle its full theta JC limited power at full rail voltage. In a class AB amp, it never has to handle much above one rail (40V, for the BDs). It may handle full theta JA limited power (a couple watts), but that’s because the junction is already up at 150. You normally wouldn’t run the (class A) VAS at enough current to be a problem with second breakdown if you used them there. For a big class A amp, you wouldnt used BD139 as a driver, you’d use another C5200 and a BD to drive that. And you would be thinking about thermals a whole lot more.
 
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#15
gary s said:
Plenty of BD139/140 in stock at Mouser, Digikey and TME in Europe.
Click to expand...
I don't live in Europe anymore... And right now, my best supplier is LCSC, nothing beats their prices and if you play it safe, there's nothing wrong with this particular Chinese supplier.
wg_ski said:
Won’t (or shouldn’t) be above +/-40V if the BDs were being considered. Wouldn’t need 120,160 or 230V transistors, but in most cases it won’t hurt anything either. Those higher voltage alternatives are usually more expensive than the generic BD139/40. And unfortunately, more likely to be fakes if you have to buy them on the gray market. So watch it.

Mouser is not necessarily available everywhere in the universe. In the free world, with a credit card, yes. But that’s not universal.
Click to expand...
Rails are +- 35V

Going to finish my design and try to simulate it with the options you guys mentioned. Will post the results.

As for Mouser, they absolutely are my favourite supplier. They are by far, at least in Europe. The best supplier on the planet, if you indeed have a credit card and deep pockets.

Credit card is not of a concern for most people, me included, but the problem is: US currency. Not every one on any part of the world can open his wallet and buy online things and pay it on US Dollars, or at least in South America. Their currencies are worth sometimes 1/10 of dollars, most of the times 1/100 of USD and I won't mention Venezuela (today 1 USD is a about 3 MILLION Bolivars). In Chile is about 1/800, and Argentina: 1/270

The least unfortunate is Brazil (where I'm currently staying), where everything is indexed to USD and local currency is at least 1/5 worth of the American counterpart. Importing from the US is simply prohibitive, so I'm stuck to the great prices and not so much quality of China.

I can get Yageo Resistors from a fraction of the price at LCSC and quality wise, I don't think Yageo are that so inferior to KOA, TE or anything else. And even buying non Asian components are way cheaper than mouser.

Yageo 470K 1% 250mW

LCSC: US$0.0112
Mouser: US$0.10

I agree, that Mouser is a great partner for hobbyists and small projects, but for someone outside Europe or US: Not so much. Specially if you're on the business and you need to import a larger components selection.

So sorry for the long text. I'll be posting results of the mentioned alternatives.
 
#16
It seems like getting quality semiconductors into South America is a problem - and will probably continue to be. Makes one wonder how serious manufacturers are doing it. Must be just deep pockets or payoffs. I know the policies are designed to keep manufacturing local, but they’ve got to get parts in there somehow. The semiconductor fabs are, for the most part, on the other side of the world.

Middlemen like Mouser aren’t going to be well-liked where importing is restricted, but they do serve a legitimate purpose and do so cost effectively for small users in the states and EU.
 
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#18
WOW... That is really weird... Last night, when I was searching for the BD's, only the BD139 from STM was available from LCSC. Both STM and ONSEMI was not available for the 139. But today, 139 both ONSEMI and STM are available, but the 140 only for the STM. Maybe tomorrow the ONSEMI will be available as well for the 140? WTF?

I've been dealing with LCSC for a while now, never had any bad experiences, but I've heard that some users had issues with non existing stock after they purchased the components

Anyway, I'm sticking to LCSC:

Mouser:
1:$0.66
10:$0.577
100:$0.443
500:$0.35

LCSC:
5:$0.2298
50:$0.1865
150:$0.168
500:$0.1448

Thanks a lot for the heads up @AIM65
 
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#19
tavares_costa said:
I don't live in Europe anymore
Click to expand...

Why oh why search for "alternatives" to cheap widely available components?

I have manufactured Guitar amps and speakers in Brazil and of course have sourced 99% of components locally, anything else is commercial suicide.
Stopped because of Covid, couldn´t shuttle Buenos Aires-Sao Paulo any more,maybe I´ll restart there next year.

Precisely because local manufactiring is protected, related components, tools, machinery, services are widely available and thriving, exact opposite of Europe and US.

You can get all BD139/140 you like at Sao Paulo Multicomercial, in the Santa Efigênia "electronics" neighbourhood.
https://www.multcomercial.com.br/transistor-db329-to126-cod-loja-4839-st-microelectronics.html
for meager R$0,90 , about 20 cents U$

Didn´t check BD140, since it must cost exact same.

EDIT: please ignore the schematic below, apparently it "stayed" from an answer in a different thread.
Can´t erase it.
 

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