Just so long as we remember to check it'll fit the need. I recently inherited a design that used some parts from the 70s and they were not up to the task. Drop-out voltages too high, gate threshold voltages too high; whatever spec could be violated was. Just because it's been used for 50 years doesn't mean it's the right part for the job
Most parts in most designs aren't anywhere close to being specification-critical. Specifying the 3904 is a great way to say "I need an NPN transistor here, and it doesn't really matter which one" (because, oh man, they can ship a lot of different things in that "3904" bin spec, and they do). So the "jellybeans" are often ideal choices.
When they are not, that is when the design engineer earns their pay.
These parts that become "the part" often have this issue relatively early into the lifecycle. The 741 op-amp is another example. They are often bad and expensive, but they are a default so people put them in.
The 2N3904 is an old friend who has never changed. I've been using him since the 80s and he's still my first choice whenever anything general-purposey comes along.
Those were originally Philips devices, but like with the American JEDEC part names, after a device with an European part name, like BC337 was registered, any semiconductor device manufacturer could sell equivalent devices.
The European part numbers provided much more information than the American part numbers.
JEDEC 2Nxxxx just told you that this is some kind of transistor or thyristor, instead of being a diode like 1Nxxxx.
BC told you that this is a silicon small-power audio-frequency transistor.
There were separate codes for other materials and for many other kinds of transistors, diodes and thyristors (for example AD = germanium high-power audio-frequency transistor, BF/BL = Si low/high-power RF transistors, BS/BU = Si low/high-power switching transistors, BR/BT = Si low/high-power thyristors, BA/BY = Si low/high-power rectifiers, BB = Si varicaps, and many others).
Motorola and some other US companies, like Texas Instruments and Fairchild, entered the transistor market very early, when they defined types like 2N2222, which became industry standards.
However, because these devices were defined early, they had rather poor characteristics. When European companies like Philips, Siemens, Thomson, SGS-ATES entered the market later, they defined transistors and other devices with improved characteristics.
Because of this, in Europe the devices with European part numbers, like BC337, were generally preferred, because they provided better analog performance, e.g. lower noise and higher bandwidth.
However nowadays this has become mostly irrelevant, because a legacy transistor vendor makes only a small number of different kinds of transistors, distinguished mainly by die size, because bigger sizes are needed to handle bigger currents. Then the transistors are packaged and marked with any of the legacy part numbers, depending on what part number the customer orders.
So while old transistors may have quite different characteristics depending on the part name, many modern transistors behave the same, regardless how they are marked.
> BC told you that this is a silicon small-power audio-frequency transistor.
BC breaks down as a silicon device, with no heater voltage, and a "triode".
If it was germanium, it would be AC <something>.
So BC548 is a silicon "triode", AC128 is a germanium "triode", and PC97 is a triode with a 300mA-rated heater (P is series connected with other valves, 300mA) in a B7G base (the 9).
"BF" might be an RF transistor although "F" was really used to mean a pentode in valves.
And those dual NPNs used in expo converters in synths might be accurately enough labeled as BCC548, similar to the ubiquitous ECC83 dual triode.
You also see this with diodes, were AA119 is a germanium small-signal diode, and BY127 is a silicon high(-ish) power rectifier diode, for example.
No. "B" is just the material (for instance "A" = Ge, "B" = Si, "C" = GaAs and related materials).
The letter that encodes the semiconductor material replaced the letter that encoded the voltage or the current used by the heating filament of vacuum tubes.
The material letter has nothing to do with the kind of device.
Examples of silicon diodes: BA (small power rectifier), BB (varicap), BY (high power rectifier), BZ (Zener diode).
It is true that some of the letters that denote kinds of devices have been inherited from the previous nomenclature of European vacuum tubes.
So C, D, F, L, used for low-power/high-power AF/RF bipolar transistors come from the letters used for low-power/high-power triodes/pentodes.
However other letters, like S, U, R, T, used for switching transistors and thyristors (a.k.a. SCRs), were new for the semiconductor device nomenclature.
Exactly, I grew up playing with BC547 and BC337s (my father was an electronics engineer) and only later found 2N2222 and 2N3904. Those were almost entirely unheard of in India.
No later than last week I was fishing in my boxes for two pieces of 2N2222 for a pet project!
Just so long as we remember to check it'll fit the need. I recently inherited a design that used some parts from the 70s and they were not up to the task. Drop-out voltages too high, gate threshold voltages too high; whatever spec could be violated was. Just because it's been used for 50 years doesn't mean it's the right part for the job
In fact, unless ubiquity in availability is a really core part of the design requirement, they almost certainly aren't the right part for the job.
Most parts in most designs aren't anywhere close to being specification-critical. Specifying the 3904 is a great way to say "I need an NPN transistor here, and it doesn't really matter which one" (because, oh man, they can ship a lot of different things in that "3904" bin spec, and they do). So the "jellybeans" are often ideal choices.
When they are not, that is when the design engineer earns their pay.
These parts that become "the part" often have this issue relatively early into the lifecycle. The 741 op-amp is another example. They are often bad and expensive, but they are a default so people put them in.
The 2N3904 is an old friend who has never changed. I've been using him since the 80s and he's still my first choice whenever anything general-purposey comes along.
BC547? 337? I think they are Texas devices, much popular too.
Those were originally Philips devices, but like with the American JEDEC part names, after a device with an European part name, like BC337 was registered, any semiconductor device manufacturer could sell equivalent devices.
The European part numbers provided much more information than the American part numbers.
JEDEC 2Nxxxx just told you that this is some kind of transistor or thyristor, instead of being a diode like 1Nxxxx.
BC told you that this is a silicon small-power audio-frequency transistor.
There were separate codes for other materials and for many other kinds of transistors, diodes and thyristors (for example AD = germanium high-power audio-frequency transistor, BF/BL = Si low/high-power RF transistors, BS/BU = Si low/high-power switching transistors, BR/BT = Si low/high-power thyristors, BA/BY = Si low/high-power rectifiers, BB = Si varicaps, and many others).
Motorola and some other US companies, like Texas Instruments and Fairchild, entered the transistor market very early, when they defined types like 2N2222, which became industry standards.
However, because these devices were defined early, they had rather poor characteristics. When European companies like Philips, Siemens, Thomson, SGS-ATES entered the market later, they defined transistors and other devices with improved characteristics.
Because of this, in Europe the devices with European part numbers, like BC337, were generally preferred, because they provided better analog performance, e.g. lower noise and higher bandwidth.
However nowadays this has become mostly irrelevant, because a legacy transistor vendor makes only a small number of different kinds of transistors, distinguished mainly by die size, because bigger sizes are needed to handle bigger currents. Then the transistors are packaged and marked with any of the legacy part numbers, depending on what part number the customer orders.
So while old transistors may have quite different characteristics depending on the part name, many modern transistors behave the same, regardless how they are marked.
> BC told you that this is a silicon small-power audio-frequency transistor.
BC breaks down as a silicon device, with no heater voltage, and a "triode".
If it was germanium, it would be AC <something>.
So BC548 is a silicon "triode", AC128 is a germanium "triode", and PC97 is a triode with a 300mA-rated heater (P is series connected with other valves, 300mA) in a B7G base (the 9).
"BF" might be an RF transistor although "F" was really used to mean a pentode in valves.
And those dual NPNs used in expo converters in synths might be accurately enough labeled as BCC548, similar to the ubiquitous ECC83 dual triode.
You also see this with diodes, were AA119 is a germanium small-signal diode, and BY127 is a silicon high(-ish) power rectifier diode, for example.
Just no.
https://en.wikipedia.org/wiki/Pro_Electron
No. "B" is just the material (for instance "A" = Ge, "B" = Si, "C" = GaAs and related materials).
The letter that encodes the semiconductor material replaced the letter that encoded the voltage or the current used by the heating filament of vacuum tubes.
The material letter has nothing to do with the kind of device.
Examples of silicon diodes: BA (small power rectifier), BB (varicap), BY (high power rectifier), BZ (Zener diode).
It is true that some of the letters that denote kinds of devices have been inherited from the previous nomenclature of European vacuum tubes.
So C, D, F, L, used for low-power/high-power AF/RF bipolar transistors come from the letters used for low-power/high-power triodes/pentodes.
However other letters, like S, U, R, T, used for switching transistors and thyristors (a.k.a. SCRs), were new for the semiconductor device nomenclature.
> 2Nxxxx just told you that this is some kind of transistor or thyristor, instead of being a diode like 1Nxxxx.
Oooh that's what it means!
But yes the European code makes (a bit) more sense
Though I never used a BS/BU code, only BD and the TIP series which might be a proprietary code
Exactly, I grew up playing with BC547 and BC337s (my father was an electronics engineer) and only later found 2N2222 and 2N3904. Those were almost entirely unheard of in India.
I think the BC548/558 were a bit more popular (though lower voltage) :)
(and I think you had it up to 546 with an ever higher voltage)
This is an interesting article on how open licensing can help ensure viability long after the original designer has left the game.
BC109 for ever!
Maybe in US. We had BC107-BC109 and BC177-BC179