I think the reason is much simpler, same as with 741 and 324 op-amps. These devices just came out at the right time. They featured prominently in the first crop of books that popularized a number of reference circuits among hobbyists and pros alike, and these reference designs have been endlessly copied since (including on the site where this article is hosted). Most people just don't know what transistor or op-amp can safely replace another transistor or op-amp in a non-trivial circuit.
In fact, for any non-trivial transistor or op-amp circuit you Google for, most of the designs you get are incredibly dated. And now, AI answers are reinforcing the same biases, so I guess we're gonna be stuck here for a long while.
I saw somebody hooked an LLM up to a SPICE implementation and also an oscilloscope directly, that seemed a fascinating way to advance circuit design.
In that way an LLM could make electronics design a lot better and not based on historical accidents as it can do a lot of testing and characterization that few people would do today.
I'm excited to set up my electronics workbench with a bus pirate and my cheap scope to do a little bit of reverse engineering.
An even simpler reason is the way the device works. Like op-amps, a BJT transistor is very much a jellybean component. They all work the same. Sure, there are edge cases like high voltage/speed and very low/high power where you'd choose something different. But in general if you have a design with a BJT[1] used in a conventional way for sensor and control stuff you can drop in another part (or matched pair if you're doing something like an amplifier) of the same polarity without worry.
A current amplifier is a current amplifier, there's not a lot of complexity until you start worrying about stuff like base capacitance and whatnot.
So, sure, "at the right time" is correct, but really any good/cheap/available BJT that arrived at that time would have won.
[1] Op-amps are even more generically jellybean-like.
The "it works" part may be true for BJTs, but I think it's a stretch for op-amps. The number of Stackexchange and Reddit threads where people are struggling to debug the quirks of these ancient chips is pretty staggering.
I dunno. An op-amp is a high-impedance differential amplifier with (conceptually) infinite gain and monotonic behavior at the crossover. Hook it up in feedback to exploit those properties and walk away. Any other chip is going to work just fine as long as you aren't violating a voltage or output current spec or whatever.
It's true that it's possible to create a design that relies on a particular chip's behavior (like trying to drive an output directly and assuming it can do it vs. using, heh, a 2N2222 to drive the load). But those are pretty uniformly treated as "bad design". Op-amps "should be" jellybeans.
But these early chips are not that. The 324 has marked crossover distortion and problems with phase reversal, both have severe input and output voltage limitations, etc. Basically, they are a pain to use, especially in single-supply circuits, and there's little reason to keep using them.
They're insanely cheap. That's why they sell. They're cheap so the volume is there so they stay cheap.
I recall that I needed some 8-pin parts a while back to test something package-related. I looked around for the cheapest part I could find and guess what... it turned out that the 358 was the absolute lowest cost thing in the world in 8 pins. Cheaper even than dummy parts with no silicon in them.
I die a little inside every time I see a 741 being used in a circuit created in the last 10 years. I'd say last 20 years, but then I'd be really dead by now!
They're cheap. They're really, really, really cheap. I once tried to design out a quad 741 a colleague had put in, because I didn't like seeing a 741-type in a modern design.
I ended up with the exact same ultimate performance and a higher cost and supply chain risk.
I don't laugh at 741s anymore. (At least, not until I've looked at the rest of the schematic.)
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.
Even 20 years ago, places like TI and ADI were offering parts that are spec-dominant over the 741. Literally every parameter on the datasheet is equal to or better than the 741, and pinout is the same.
Twenty? Try forty. These things don't get chosen for performance reasons. They get chosen by:
1. Inexperienced or simply bad designers (this is real, sadly)
2. Designers minimizing cost or maximizing part availability (this is 99% of the volume these days: you just need something that does the function, and pretty much anything will do)
3. Designers who had them lying around in the parts bin when they got the circuit to work on the bench... and when it works well and cheaply you stop asking questions and ship it! (and yes the word "well" is doing some very heavy lifting there)
Also, nobody counterfeits 3904s and 741s and 324s. They're so easy to meet spec on that you can just ship them as genuine with your own label on top. A fair bit of counterfeits of other chips are 358s with fake top markings. That is the kind of cockroach these guys are!
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.
A somewhat little know part is a "pre-biased transistor": this is a bipolar transistors with built-in resistors, and will often work as a drop-in replacement for a logic-level MOSFET (like 2n7000), but is an order of magnitude cheaper.
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.
>Today, the metal-can 2N2222 is still available from Mouser and DigiKey at around $1.88 per unit, while mil-spec hermetic TO-18 versions sell for upwards of $60 each.
$60 per transistor?? The military is getting ripped off by its suppliers.
Even the DigiKey price is nuts, you can get functionally identical transistors from China for less than a penny each.
Well, kinda. The value is in meeting the spec, yes, but the "certifiable" part is very often a subset of the actual spec. Sort of like in software how someone will inevitably depend on every feature of a public API (including the defects), a lot of early military electronics depend on implementation details of their component processes, usually by accident. The cost for semiconductor companies is not meeting the spec, it's keeping a production line from the 1960s running exactly the same way for a single customer who buys a handful of parts every year.
The problem with Chinese semiconductors isn't performance or meeting specs, at least not these days. It's counterfeits, life expectancy of the source companies, and the obvious risk of basing your supply chain on a foreign political actor that can leverage this dependency against you.
I wouldn't be so quick to make guarantees. There's cheaper spec-equivalent devices, sure, but a frequent and recurring feature of military hardware prior to the 2000s is an unexpected dependence on non-spec device characteristics. I've seen seemingly inconsequential cost-saving process tweaks identified as the root cause for novel testing failures for more than one ancient US military project.
Setting aside that approximately no one is shooting down quadcopters with missiles, that quadcopters and missiles are entirely different categories of weapon with substantially different range/payload/response time targets, and that the availability logistics and acceptable failure rates of paramilitary gangs and impoverished former Soviet belligerents from whom we are likely drawing conclusions about drone warfare economics are maybe just a step or two below the average US military procurement contract requirements; and charitably interpreting your argument as a generalization that repurposed consumer-grade electronics offers a cost reduction over military-grade selections for equivalent performance: true in most modern cases. The US has plenty of cheap domestic options for seemingly pricy problem domains, just ask SpaceX. SOTA in aerospace and defense routinely uses commercial products to great effect. To the extent that shelling out for a $60 military-grade 1960s transistor instead of a $0.06 commercial equivalent is a problem for the US military, it is downstream of enormous legacy cold war capital investment in technology that was novel for its time but is comparatively brittle by modern standards. This is still a problem, to be clear, but a small one in the grand scheme of US military spending.
Individual transistors are generally durable devices. If anything fails over that range it will be the battery, the mechanical parts, or the PCB itself.
Consumer electronics are perfectly serviceable for military use. Other countries are building very effective weapons at much lower prices by taking advantage of this.
That is the DigiKey price for the metal can version. Plastic packaged versions can be bought for ten cents each individually or 2.443 cents each in quantity 1000. Buy all you like - there are over 18000 in stock ready to be at your door the next day.
I think the reason is much simpler, same as with 741 and 324 op-amps. These devices just came out at the right time. They featured prominently in the first crop of books that popularized a number of reference circuits among hobbyists and pros alike, and these reference designs have been endlessly copied since (including on the site where this article is hosted). Most people just don't know what transistor or op-amp can safely replace another transistor or op-amp in a non-trivial circuit.
In fact, for any non-trivial transistor or op-amp circuit you Google for, most of the designs you get are incredibly dated. And now, AI answers are reinforcing the same biases, so I guess we're gonna be stuck here for a long while.
I saw somebody hooked an LLM up to a SPICE implementation and also an oscilloscope directly, that seemed a fascinating way to advance circuit design.
In that way an LLM could make electronics design a lot better and not based on historical accidents as it can do a lot of testing and characterization that few people would do today.
I'm excited to set up my electronics workbench with a bus pirate and my cheap scope to do a little bit of reverse engineering.
An even simpler reason is the way the device works. Like op-amps, a BJT transistor is very much a jellybean component. They all work the same. Sure, there are edge cases like high voltage/speed and very low/high power where you'd choose something different. But in general if you have a design with a BJT[1] used in a conventional way for sensor and control stuff you can drop in another part (or matched pair if you're doing something like an amplifier) of the same polarity without worry.
A current amplifier is a current amplifier, there's not a lot of complexity until you start worrying about stuff like base capacitance and whatnot.
So, sure, "at the right time" is correct, but really any good/cheap/available BJT that arrived at that time would have won.
[1] Op-amps are even more generically jellybean-like.
The "it works" part may be true for BJTs, but I think it's a stretch for op-amps. The number of Stackexchange and Reddit threads where people are struggling to debug the quirks of these ancient chips is pretty staggering.
I dunno. An op-amp is a high-impedance differential amplifier with (conceptually) infinite gain and monotonic behavior at the crossover. Hook it up in feedback to exploit those properties and walk away. Any other chip is going to work just fine as long as you aren't violating a voltage or output current spec or whatever.
It's true that it's possible to create a design that relies on a particular chip's behavior (like trying to drive an output directly and assuming it can do it vs. using, heh, a 2N2222 to drive the load). But those are pretty uniformly treated as "bad design". Op-amps "should be" jellybeans.
But these early chips are not that. The 324 has marked crossover distortion and problems with phase reversal, both have severe input and output voltage limitations, etc. Basically, they are a pain to use, especially in single-supply circuits, and there's little reason to keep using them.
They're insanely cheap. That's why they sell. They're cheap so the volume is there so they stay cheap.
I recall that I needed some 8-pin parts a while back to test something package-related. I looked around for the cheapest part I could find and guess what... it turned out that the 358 was the absolute lowest cost thing in the world in 8 pins. Cheaper even than dummy parts with no silicon in them.
That's how cheap they are.
I die a little inside every time I see a 741 being used in a circuit created in the last 10 years. I'd say last 20 years, but then I'd be really dead by now!
They're cheap. They're really, really, really cheap. I once tried to design out a quad 741 a colleague had put in, because I didn't like seeing a 741-type in a modern design.
I ended up with the exact same ultimate performance and a higher cost and supply chain risk.
I don't laugh at 741s anymore. (At least, not until I've looked at the rest of the schematic.)
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.
These days there's also a wide variety of manufacturers making them including very sketchy counterfeiters.
So there are TONS of pin-compatible-ish parts from different manufacturers that have related specs with a ton of variation.
Even 20 years ago, places like TI and ADI were offering parts that are spec-dominant over the 741. Literally every parameter on the datasheet is equal to or better than the 741, and pinout is the same.
Twenty? Try forty. These things don't get chosen for performance reasons. They get chosen by:
1. Inexperienced or simply bad designers (this is real, sadly)
2. Designers minimizing cost or maximizing part availability (this is 99% of the volume these days: you just need something that does the function, and pretty much anything will do)
3. Designers who had them lying around in the parts bin when they got the circuit to work on the bench... and when it works well and cheaply you stop asking questions and ship it! (and yes the word "well" is doing some very heavy lifting there)
Also, nobody counterfeits 3904s and 741s and 324s. They're so easy to meet spec on that you can just ship them as genuine with your own label on top. A fair bit of counterfeits of other chips are 358s with fake top markings. That is the kind of cockroach these guys are!
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.
A somewhat little know part is a "pre-biased transistor": this is a bipolar transistors with built-in resistors, and will often work as a drop-in replacement for a logic-level MOSFET (like 2n7000), but is an order of magnitude cheaper.
https://www.digikey.com/en/products/detail/diotec-semiconduc...
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.
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.
Just no.
https://en.wikipedia.org/wiki/Pro_Electron
> 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
[flagged]
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.
No later than last week I was fishing in my boxes for two pieces of 2N2222 for a pet project!
BC109 for ever!
Maybe in US. We had BC107-BC109 and BC177-BC179
>Today, the metal-can 2N2222 is still available from Mouser and DigiKey at around $1.88 per unit, while mil-spec hermetic TO-18 versions sell for upwards of $60 each.
$60 per transistor?? The military is getting ripped off by its suppliers.
Even the DigiKey price is nuts, you can get functionally identical transistors from China for less than a penny each.
The value is in certifiably meeting the spec, not the function.
You shouldn't have to think very hard about why the military does not want to buy parts from China.
Well, kinda. The value is in meeting the spec, yes, but the "certifiable" part is very often a subset of the actual spec. Sort of like in software how someone will inevitably depend on every feature of a public API (including the defects), a lot of early military electronics depend on implementation details of their component processes, usually by accident. The cost for semiconductor companies is not meeting the spec, it's keeping a production line from the 1960s running exactly the same way for a single customer who buys a handful of parts every year.
The problem with Chinese semiconductors isn't performance or meeting specs, at least not these days. It's counterfeits, life expectancy of the source companies, and the obvious risk of basing your supply chain on a foreign political actor that can leverage this dependency against you.
I guarantee you the cheaper transistor works just fine.
This is why quadcopter drones, built using uncertified consumer parts, are cheaper than the missiles to shoot them down.
Sure, they can't buy it from China, but China and its allies can. This is a problem for the US.
I wouldn't be so quick to make guarantees. There's cheaper spec-equivalent devices, sure, but a frequent and recurring feature of military hardware prior to the 2000s is an unexpected dependence on non-spec device characteristics. I've seen seemingly inconsequential cost-saving process tweaks identified as the root cause for novel testing failures for more than one ancient US military project.
Setting aside that approximately no one is shooting down quadcopters with missiles, that quadcopters and missiles are entirely different categories of weapon with substantially different range/payload/response time targets, and that the availability logistics and acceptable failure rates of paramilitary gangs and impoverished former Soviet belligerents from whom we are likely drawing conclusions about drone warfare economics are maybe just a step or two below the average US military procurement contract requirements; and charitably interpreting your argument as a generalization that repurposed consumer-grade electronics offers a cost reduction over military-grade selections for equivalent performance: true in most modern cases. The US has plenty of cheap domestic options for seemingly pricy problem domains, just ask SpaceX. SOTA in aerospace and defense routinely uses commercial products to great effect. To the extent that shelling out for a $60 military-grade 1960s transistor instead of a $0.06 commercial equivalent is a problem for the US military, it is downstream of enormous legacy cold war capital investment in technology that was novel for its time but is comparatively brittle by modern standards. This is still a problem, to be clear, but a small one in the grand scheme of US military spending.
> I guarantee you the cheaper transistor works just fine
From -50C to 70C? How much shock & vibration can it withstand?
> From -50C to 70C? How much shock & vibration can it withstand?
Regular automotive range parts are rated for -40 to +125 with the ability to withstand endless vibration and shock.
There is no doubt in my mind that any fab outside of America can make the leap from automotive to military spec.
Individual transistors are generally durable devices. If anything fails over that range it will be the battery, the mechanical parts, or the PCB itself.
Consumer electronics are perfectly serviceable for military use. Other countries are building very effective weapons at much lower prices by taking advantage of this.
That is the DigiKey price for the metal can version. Plastic packaged versions can be bought for ten cents each individually or 2.443 cents each in quantity 1000. Buy all you like - there are over 18000 in stock ready to be at your door the next day.
https://www.digikey.com/en/products/detail/shenzhen-slkormic...
The keyword is "trust".