Hep 553 Transistor

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As the Lnsiduous integrated-circuit chip makes its way ever deeper into the heart of electronics, more and more construction articles are devoted to IC projects. While some purists (probably the same ones who used to build their own vacuum tubes) may object to this trend, it's probably all for the better — because the ICs result in more uniform and predictable circuits and permit us to homebrew devices which only a few years ago were simply too much trouble for any but the most dedicated of homebrewers.

But there is one thing wrong with ICs: there are just too many different kinds of them on the market. The same thing is going on that happened when vacuum tubes made their debut, and much more recently with transistors. Every different manufacturer has his own set of identification numbers, and most of the EC makers concentrate on original-equipment-manufacturer sales so that their products are not the easiest of things to find in the neighborhood parts house.

This means that many worthwhile projects simply never get built by many of us, because the particular IC which is at the heart of the project is difficult for us to obtain.

Fortunately, at least one major manufacturer of ICs has recognized this problem, and is marketing a much-simplified portion of his product line to hobbyists, experimenters, and professionals through the standard parts-house outlets.

What's more, every one of the ICs in this line can substitute for several other types of ICs in both the manufacturer's regular product series, and those of other IC makers. All that's necessary, then, to make many projects feasible is a cross-reference table (like the popular transistorsubstitution books) — and that's what this article is all about.

The manufacturer involved is Motorola, and the product line is called "HEP" (for hobbyist, experimenter, professional — the three classes of users for whom the line is intended). The HEP line contains many semiconductors in addition to IC chips, but here we're interested only in the ICs. Since additions to the line are constantly being made, this may not cover all HEP ICs by the time it reaches print, but it does describe all which are in catalog HMA 35 (released in mid-1970).

Four classes of ICs are included: three of these are digitals or computer-type circuits, and the fourth is linears or amplifier circuitry.

The three families of digital ICs include one group of emitter-coupled logic units and two groups of "TRL" devices; the two families of RTL are "milliwatt" and "medium power" units.

Most published circuits using digital ICs are built around medium—power RTL devices, since the first inexpensive such ICs were in this family.

The four families in the HEP line are: HEP 553, HEP 554, HEP 556, and HEP 558, emitter-coupled logic digitals?s; HEP 570, HEP 571, HEP 572, and HEP 584, medium-power RTL; HEP 580, HEP 581, HEP 582, and HEP 583, milliwatt RTL; and HEP 590, HEP 591, HEP 592, and HEP 593, linear.

We won't go into the ECL (553-558) very deeply, since ECL logic circuits differ somewhat from the more familiar ones.

In RTL, the 570-572 are 14-prn dual-inline packages (DIPs) and the 580—584 are in 10-Iead TO-5 transistor cans (HEP 453 is the flatpack socket, while HEP 451 fits the 10-iead units).

The HEP 570 is a quadruple 2-input nor gate (four .identical 2-input gates in one package but electrically independent). The HEP 571 is a dual buffer. The HEP 572 is a dual J - K flip-flop.

The HEP 584, final member of this medium-power RTL family is a dual 2-input nor gate, equivalent to halfof a HEP 570.

The HEP 580 is a dual 2—input nor like the HEP 584 except that the 580 is a milliwatt unit requiring, and producing, less power. The HEP 581 is a 4—input nor while the HEP 582 is a dual buffer but has two inputs to each buffer permitting it to be used as a dual 2-input nor also. (The 581 has an inverter built in which permits it to be used as a 4 input nor also.) The final member of the milliwatt RTL family, the HEP 583, is a dual J-K flip-flop.

The linear circuits include a high-

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