transistor quality?

[harps]

hi : )

i am looking to buy some transistors for turning on relays and leds. i usually use 2n3904's they seem to work quite nicely.

i find on the RS site there are

ON Semiconductor "General Purpose Transistors, 2N3904ZL1G" @ 200 for .025p each ( £5)
or
magnatec or fairchild at 20-24p each , near ten times more expensive. if i would buy a small amount of course, i just wonder if there is any real diffrence, maybe the brand names are a good indication?

https://uk.rs-online.com/web/c/?searchTerm=2N3904&sra=oss

i would like good quality of course, i just wonder what you guys look at to decide?

thanks: )

 

[JimB]

Probably just the effect of large quantity pricing.

If the fairchild 3904s were offered in packs of 200 I think that the price would be considerably lower.

JimB

On edit
Look at the fairchild 2n3904s, in quantities of 50 the price is down form 24p to 10p each.

 

[harps]

thanks jim.

i think , just to be sure, as i hope my circuit lasts for many years, i shall buy 50 of the fairchild. : )

 

[colin55]

On eBay you can get them post-free.

 

[dr peppers]

The number of the transistor tells you all about it in most cases, enter the pre and suffix into google and get the datasheet, you can get different voltage ratings and different temperature ratings of the same device and this can affect price.

However as mentioned the retailer also has a lot to do with it, RS shift boxes of them and can afford to sell them cheap, a hobbyist stock holder only sells low quantities and has to pay someone to count them out and handle all the associated admin.

Ebay is a good source if you dont want traceability, there are lots of sellers doing surplus and bankrupt stock for peanuts, they get them for next to nowt and sell them for peanuts.

 

[Miles Prower]

When it comes to transistors, it doesn't really matter what type you use so long as you stay within the appropriate voltage and current specs. It's a high gain device, and circuit performance is independent of active device characteristics. The only cases where it would make a difference is if you need some special property, such as an unusually low noise figure, or high voltage operation, or operating at unusually high frequencies.

 

[bountyhunter]

Military grade transistors are very expensive, but commercial grade are all basically the same.

 

[Lund_Pa]

MIL Spec is your best bet. But you will pay dearly for them. I remember buying SMT resistors for a mil/aerospace company at $20 each.

 

[Miles Prower]

Military grade transistors are very expensive, but commercial grade are all basically the same.

Military grade usually means special hardening against radiation. If you're not going to use them in such an environment, it's really not necessary. Most projects, especially of the variety mentioned in the OP, won't need uber special transistors.

 

[KeepItSimpleStupid]

Why not use the ULN2003 or ULN200x series of relay driver IC's. https://www.electro-tech-online.com/custompdfs/2012/03/ulq2004a.pdf The IC has been around for years. it includes the suppression diodes. There is a 8 driver version available too. I forget the number.

The nice part about the driver is that with the input (open circuit) the relay is OFF. You need to select the right version for the logic family your using.

You also might want to look at a "digital transistor".

 

[crutschow]

Military grade usually means special hardening against radiation. If you're not going to use them in such an environment, it's really not necessary. Most projects, especially of the variety mentioned in the OP, won't need uber special transistors.

Standard military grade semiconductors are not hardened against radiation. That is an added (and very expensive) option only for those used in specific space or other applications where the device is known to be exposed to damaging radiation. But military grade generally have better reliability, hermetic metal packaging, and a higher operating temperature range than commercial devices.

 

[bountyhunter]

Unless you are launching a satellite, the cost of mil grade (JANTX) devices is ridiculous.

 

[tvtech]

However as mentioned the retailer also has a lot to do with it, RS shift boxes of them and can afford to sell them cheap, a hobbyist stock holder only sells low quantities and has to pay someone to count them out and handle all the associated admin.

Ebay is a good source if you dont want traceability, there are lots of sellers doing surplus and bankrupt stock for peanuts, they get them for next to nowt and sell them for peanuts.

Get this right....RS don't sell cheap components. All are up to Manufacturer spec. At least. No rubbish there....

Excellent parts and definitely not cheap. Genuine components.

Don't mislead people dr peppers. Get your facts right.......

Regards,
TV Tech

 

[dr peppers]

You misunderstood me I'm afraid tvtech.

I said RS sell them cheap, not that they are cheap components, RS comply with several european directives and ISO standards and ceratinly dont sell 'cheap' components, you are right RS are a reputeable company, if they were not I wouldnt be spending a thousand quid a month with them, I have a purchasing manager account with RS components.

Please get your facts right before you shout at me.

 

[tvtech]

You misunderstood me I'm afraid tvtech.

I said RS sell them cheap, not that they are cheap components, RS comply with several european directives and ISO standards and ceratinly dont sell 'cheap' components, you are right RS are a reputeable company, if they were not I wouldnt be spending a thousand quid a month with them, I have a purchasing manager account with RS components.

Please get your facts right before you shout at me.

Sorry for shouting....my bad

Just trying to clarify things...heck RS could of been Radio Shack....thinking about that last night.....

Be good

Cheers,

TV Tech

 

[audioguru]

Is "RS" Radio Spares in the UK or is it RadioShack in USA?
I think when RadioShack was still in Canada they sold "seconds" which were from the garBage bin of a manufacturer.
Now I think their expensive parts are cheap Oriental copies that might or might not work.

 

[bountyhunter]

Is "RS" Radio Spares in the UK or is it RadioShack in USA?
I think when RadioShack was still in Canada they sold "seconds" which were from the gargage bin of a manufacturer.

They have been doing the same thing here in the USA for many decades.

 

[JimB]

In the UK, "RadioSpares" became "RS Components" about 40 years ago.

We never have had (as far as I know) "Radio Shack" as such, in the UK that organisation was always known as "Tandy", selling the same stuff as Radio Shack in the USA and Canada.

When someone in the UK mentions RS, they mean RS Components, a supplier of good quality (and expensive) stuff.

JimB

 

[audioguru]

I think Maplin in the UK sells the same cheap junk at extremely high prices as RadioShack in the USA.
Somebody on one of these forums recently posted the Tandy or InterTan link between a UK parts distibutor and RadioShack but I didn't save it because I am not a Brit and I am not an American.

 

[Miles Prower]

Is "RS" Radio Spares in the UK or is it RadioShack in USA?
I think when RadioShack was still in Canada they sold "seconds" which were from the gargage bin of a manufacturer.
Now I think their expensive parts are cheap Oriental copies that might or might not work.

Radio Shack has long specialized in selling "cosmetic rejects". It's not that they're necessarily inferior, just mismarked or with some other defect that doesn't affect the electronic properties. They also package somewhat related parts in those fifteen packs of "transistors anonymous". They still work just fine.

"Cheap Oriental copies" are frequently counterfeits.