Kazizilkree I used my time as a student as an example because it happened to be where I first saw an HC device. Balanced mixers had advantage. 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 signal bipolar transistor in an audio darasheet could be just about any small signal transistor, so long as it was NPN, and even then a PNP could often work as long as you made adjustments. Datasheet pdf. Equivalent They wanted to use what they had, or what they could scrounge.
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March 21, As a fresh-faced electronic engineering student while the 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: 74HC. Exotic, even. Thus an association was formed, when you want a quick logic function then 74HC is the modern one to go for.
Launched in the mists of time when dinosaurs probably still roamed the earth, this static-sensitive four-pin TO72 found a home in a huge variety of RF amplifiers, 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 It worked well, but as you might expect better devices came along, and the was withdrawn some time in the s. Because even today, thirty years after the shuffled off this mortal coil, you can still find people specifying it.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: a plea for designers to do their homework. 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. 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.
There is of course also a slightly macabre alternative scenario.
40673 MOSFET. Datasheet pdf. Equivalent
40673 Dual Gate Mosfet Transistor
The Curse Of The 40673: Zombie Components That Refuse To Die