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
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 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
This is an interesting article on how open licensing can help ensure viability long after the original designer has left the game.
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.