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BC Transistors...

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Electric Rain

New Member
I want to do a project that requires BC559 transistors. I have also run across many other schematics that require BC transistors... and I haven't been able to find them almost anywhere. And I do know that sometimes parts have different names for different areas of the world and everything else. So, I would like to know if "BC" is for like... Europe or something. :? :? :? Ok I don't really know what I'm talking about I guess... but I live in the US. So could someone (if you get what I'm trying to say,) explain to me how it all works with BC transistors please? :?: :? Thanks.

Rain

P.S. :oops: I don't know how it works. :lol:
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Electric Rain said:
I want to do a project that requires BC559 transistors. I have also run across many other schematics that require BC transistors... and I haven't been able to find them almost anywhere. And I do know that sometimes parts have different names for different areas of the world and everything else. So, I would like to know if "BC" is for like... Europe or something. :? :? :? Ok I don't really know what I'm talking about I guess... but I live in the US. So could someone (if you get what I'm trying to say,) explain to me how it all works with BC transistors please? :?: :? Thanks.

Rain

P.S. :oops: I don't know how it works. :lol:

It's the standard European system and is called 'Pro-Electron'.

The first letter indicates the semiconductor material.
A = Germanium.
B = Silicon.
Plus various other specialised ones.

The second letter indicates the function.
A = detection diode, high speed diode, mixer diode.
B = varicap didode.
C = transistor for small AF applications.
D = power transistor for AF applications.
Again, plus various others.

A BC559 is a PNP silicon small signal AF transistor, it's in a plastic encapsulation, and it's a particularly low noise device, intended for front ends in microphone amplifiers and tape recorders.
 

Ravi

Member
For your information,
Near equivalent of BC559 - BC558,BC179 (metal case)
Complement is BC549

Some parameters of BC559
Ic(max) - 100mA
Vceo(max)-30V
Pt(max)-625mW
hfe-250
@Ic-2mA
Ft(typ) - 250Mhz
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Electric Rain said:
Wow, thanks guys! :D Mostly you, Nigel Goodwin. If it helps, this is the project I need those transistors for: https://home.t-online.de/home/stephan.hans/n64.htm So does anyone know where I could find those transistors or ones the you're SURE will work just as well in place of them?

That's a very non-critical application, any small PNP transistor would be fine - personally the two small transistors I always use are the BC107 (NPN) and BC177 (PNP), they are metal cased - rather than plastic. They are the original versions of the BC547 and BC557, which use plastic encapsulation. Simply use whichever you can get - I notice the design actually quotes 'standard PNP'.

Almost all transistor applications are fairly non-critical, in fact correct design is intended to make it so - it's only when you are choosing a device for a particular characteristic that they become critical. The most common reason is probably output transistors, these are normally chosen for specific reasons - maximum voltage, current, and dissipation.
 

Johnson777717

New Member
You may want to try Digikey.com. I just ordered a couple BC series transistors from them. They may have the one you're looking for. Good luck!
 

Gandledorf

New Member
I have a question about transistors, in a similar vein. I ran across a page on futurlec: https://futurlec.com/TransGenSpec.shtml which does a quasi-decent job of comparing some common transistors. However, I'm not 100% sure how to read the specs. Could you help decipher them? I've listed them below with my "best guesses"

Ic(mA) - Maximum current it can safely pass?

Pd(mW) - Power dissipation?

Vce(max) - Max collector - emitter voltage?

Vcb(max) - Max collector - base voltage?

hfe - No clue

@ Ic - No clue

FT (MHz) - Switching speed?

Thanks in advance!
 

k7elp60

Active Member
transistor specifications

Hfe= static forward current transfer ratio(common-emitter)Collector current/base current. Usually specified at a certain collector current.

Ic= collector current, can be specified as maximum continous

Ft= transition frequency or frequency at which small-signal forward current transfer ratio(common-emitter) extrapolates to unity.
 

Gandledorf

New Member
Re: transistor specifications

k7elp60 said:
Hfe= static forward current transfer ratio(common-emitter)Collector current/base current. Usually specified at a certain collector current.

Ic= collector current, can be specified as maximum continous

Ft= transition frequency or frequency at which small-signal forward current transfer ratio(common-emitter) extrapolates to unity.

Thanks for the answers, they were very helpful, but I am still a little shaky on Hfe. For instance, on a PN2222, it lists the Hfe as:
Test Condition Min Max
...
IC = 1.0 mA, VCE = 10 V 50 300
...

What does this mean? How do I compare this to my circuit which has 1 Amp current @ 5V Vce?
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Re: transistor specifications

Gandledorf said:
What does this mean? How do I compare this to my circuit which has 1 Amp current @ 5V Vce?

You don't very well - gain is always quoted at a specific value of current (presumably where it looks best!). If you really want to know the gain of your transistor at 1A you would need to measure it.

However, circuits are almost always designed to be fairly tolerant of transistor gain - individual transistors of the same time can have wildly different gains - if you design a circuit that is critical for gain, you have to adjust the component values (or at least one of them) for every single one you make. This has been done in the past - with resistors labelled 'adjust value for x volts at test point y' on service manuals, but I've not seen it for years now.
 

Gandledorf

New Member
Re: transistor specifications

Nigel Goodwin said:
Gandledorf said:
What does this mean? How do I compare this to my circuit which has 1 Amp current @ 5V Vce?

You don't very well - gain is always quoted at a specific value of current (presumably where it looks best!). If you really want to know the gain of your transistor at 1A you would need to measure it.

However, circuits are almost always designed to be fairly tolerant of transistor gain - individual transistors of the same time can have wildly different gains - if you design a circuit that is critical for gain, you have to adjust the component values (or at least one of them) for every single one you make. This has been done in the past - with resistors labelled 'adjust value for x volts at test point y' on service manuals, but I've not seen it for years now.

Am I fairly sure that it will be in the vicinity of 1? I'm only trying to use the transistor as a switch, and just want it to pass my current to fuel my IR beam.
 

k7elp60

Active Member
transistor specs

Well my National Semiconductor data books lists one of the charastics of the PN2222, Hfe 100-300 @ Ic of 150 Ma. What that means is that with a collector current of 150Ma the gain could vary between 100 and 300 with 100 being the minimum. Looking in a Motorola data book for the metal case equivalent of the PN2222 or the 2N2222 it shows the same specs.
But like Nigel said if you want to know the gain at a certain Ic you need to measure it.
When I design a transistor circuit I design the biasing for the minimum hfe,
as a result any transistor of that number will work in the circuit.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Re: transistor specs

k7elp60 said:
When I design a transistor circuit I design the biasing for the minimum hfe,
as a result any transistor of that number will work in the circuit.

In the circuit under discussion, switching an IR LED with something like 1A pulses, using a small transistor, I would like to see it really turned on hard!. To that end in my original design I used a 330ohm resistor feeding the base - providing about 13mA base drive.
 
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