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As a fresh-faced electronic engineering student while modfet first Gulf War was raging in a far-off desert, I learned my way through the different families of 74 logic at a university in the North of England. At the time, there was an upstart on the scene: Thus an association was formed, when you want a quick logic function then 74HC is the modern one to go for.
But what prompted this piece was a far more egregious example of an old component still being specified: Launched in the mists of time when dinosaurs probably mosget roamed the earth, this static-sensitive four-pin TO72 found a home in a huge variety of RF 40763, oscillators, and mixers.
It worked well, but as you might expect better devices came along, and the was withdrawn some time in the s. Because even today, thirty years after the shuffled off this mortal coil, you can still find people specifying it. Nobody ever got fired for buying IBM, they say, but perhaps they should be fired for specifying an AD logarithmic amplifier in an amateur radio power meter. Sometimes there are components for which there are no perfect replacements.
Germanium point-contact diodes, for example. Hang on, this is Hackaday. OK, maybe germanium diodes are an edge case and the examples above have a radio flavour, but you get the picture. What the full-blown rant in the previous paragraphs has been building up to is this: An Apple I replica like the Mimeo 1 needs old logic chips for artistic purposes. Big paper-bound books the size of telephone directories were our only window into the exciting world of electronic components.
These publications were our only window into the world of electronic components. They contained significant excerpts from semiconductor data sheets, and we read their wealth of information from cover to cover. We knew by heart what each device was capable of, and we eagerly devoured each new tidbit of information as it arrived.
The Disappearing Dual Gate MOSFET
In short, when we specified a component, we did so with a pretty good knowledge of all the components that were available to us.
By comparison, nowadays we can quickly buy almost any device or component in production from a multitude of suppliers. The WWW allows us to find what we need in short order, and the miracle of global distribution means that we can have it delivered within 48 hours almost wherever we live.
Printed catalogs still exist, but the sheer volume of information they contain forces brevity upon their entries and expands the size of the publication to the point at which it becomes an unwieldy work of reference.
We therefore tend to stick with the devices and components we know, regardless of their cost or of whether they have been superseded, and our work is poorer for it.
The Curse Of The 40673: Zombie Components That Refuse To Die
There is of course also a slightly macabre alternative scenario. Maybe not feasible for mass production, but sure as hell no problem for any amateur building a circuit with only 4067 handfull of these…. All of your bases ARE belong to us.
My understanding is that they have a reasonably good NF and they allow you to build a combination mixer-amplifier in mosfe single device. Of course, if you know of a good candidate for replacing theplease share the details. Manufacturer mostet and part numbers would be better. I used it a fair bit. I bought a few last-buys. That line was ambiguous. Transistors came along, and early shortwave radios were often lousy, the bipolar transistors overloaded too easily.
In the early omsfet, the JFET came along, those were seen as less prone to overload. The second gate also made it easy to control the gain when used as an RF amplifier. Yes, noise figure factored in, at least if you were doing something on VHF or higher.
Circabipolar transistors also had improved noise figure. Use those Schottky diodes that arrived in the later sixties, and use four if them in a balanced mixer, often a better choice for an overload resistant mixer. These were balanced mixers, the extra transistors irrelevant because it was in an IC. Balanced mixers had advantage. Not perfect, but acceptable for a lot of uses. So that may no longer be a source, especially if you want leads. Some FM broadcast band tuners used them, so maybe car radios are a source.
But there do appear to be some parts that I would try to sub for the in an old receiver design: A bit late but anyway, a mosfet like the can be swapped with two N jfets in cascode configuration just like in these example:.
As a mixer with LO input: I actually try to use as few different components as possible, to reduce storage requirements and simplify design. Same goes for capacitors: I only buy 1 nF, 10 moseft, nF etc. I am guilty of rarely using op amps, and replace them with transistors whenever possible: This is probably leftover from my war years: And I love my germanium diodes — they allowed me to listen to crystal radio when electricity was out, and batteries were expensive or unobtainable.
Information rich and knowledge poor is probably going to be the biggest obstacle in mpsfet next few generations. Inverters are not particularly space constrained. Conversely, making inverters cheaper actually has a huge effect on the market. Inverters are a percentage of the hardware cost of a PV installation, and getting that price down DOES directly correlate into more rooftop solar. Granted, the AD part is a much better chip. The 45 dB range 8 bits in voltage devices are dirt cheap and super common.
The most expensive single chip I use today is the AD Get a 1N82 if you wanted better frequency response, thy were found in UHF tv tuners. Even inI went through an RCA price list and found one that was cheaper, I guess it was the 4N, something like that. Someone would pick a device based on specs or availability, and write about mosget project. Others would use the same device, because someone had chosen it.
An alternative is that the 40637 places somehow chose certain parts, which then found their way into projects. There was a vast selection, but hobbyists used a small subset, because the hobby suppliers were easier to del with, as well as the ubiquitous Radio Shack. The hobbyist, like the supplier, could keep a limited selection around, yet build anything within a certain level of specs.
The beginner was at the mercy of the parts list, buying that expensive HEP IC because he wanted to follow the article exactly out of fear of making a mistake, not realizing the author specified that HEP replacement line part because it was very available. But a cheap opamp was the same part. You moved further into the hobby and learned where you could substitute parts, you came to know the familiar solid state devices so you knew that diode was germanium and needed germanium, but that small NPN signal bipolar transistor in an audio oscillator could be just about any small signal transistor, so long as it was NPN, and 4073 then a PNP could often work as long as you made adjustments.
I would add my own observation that if digital logic can be done with NAND or NOR gates alone, analog can be reduced to relatively few parts as well. I thought is was diode, cathode, electrode, overload, generator, oscillator. Make a circuit with me. BF, unless my memory fails me. There were always two camps. One wanted to be able to buy the exact parts specified, preferably at Radio Shack.
Those people probably bought the kit if it was available. The other camp wanted cheap. They wanted to use what they had, or what they could scrounge.
They needed to know what was going on in mosfte circuit, and the general specs of the semiconductors.
, Tube ; Röhre ID, Transistor
Mksfet ICs came along, that got more complicated, especially as time went on. You had to buy the kit, or hope the author would supply the IC. The window for scrounging is closing.
You could pull roofing filters out of them, and crystals to convert from there to KHz, and complete KHz fm if strips. Really great UHF front end components. Now all gone, the average cellphone today has no useful parts.
Cordless phones have moved up in frequency, and are using larger scale integration, a lot less useful for reusing the parts. But then again the young generation have opportunities we never came near. Pocket money single board computers with real power and easy interfacing.
If I specify a transistor with a low price and an equivalent substitute I can be sure that my employer will be mozfet to buy that part well into the future. For me to do good work I have to have a good concept moxfet the parts catalog and keep up with new parts from suppliers and the state of the industry.
The big retailers still have catalogs. So blindly switching from HC to AC is a bit dangerous. I guess it comes down to what you mean by replacement. Yes, a 3v3 family is not a drop-in replacement mosfer a 5v part. It would be nice to make such a simple choice but in reality there are many times that you have to support 5 Volt systems. Extremely useful and they are dirt-cheap. I use a as a mixer as it happens, and in my application you start to hear the performance tail off somewhere above 10MHz with the HC part.
It completely fails at about 70MHz. I use HC parts as level translators with mixed 3v3 and 5v logic parts because there a good cheap option and do the job well.