3 ms·

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

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.

ajross 6mo ago
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.
- chromacity 6mo ago
  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.
  - ajross 6mo ago
    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.
    - chromacity 6mo ago
      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.
      - exmadscientist 6mo ago
        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.
colechristensen 6mo ago
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.
HeyLaughingBoy 6mo ago
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!
- exmadscientist 6mo ago
  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.)

ajross 6mo ago

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.

chromacity 6mo ago
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.
- ajross 6mo ago
  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.
  - chromacity 6mo ago
    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.
    - exmadscientist 6mo ago
      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.

colechristensen 6mo ago

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.

HeyLaughingBoy 6mo ago

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!

exmadscientist 6mo ago
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.)