# IC seriesElectronics guide > Digital integrated circuits II > IC series

For most people, there are two families of ICs that are used in digital electronics. The first is a very easy-to-handle variety (in other words, they can’t be easily damaged). On the other hand, they require a stable operating voltage of 5 V, which isn’t all that easy to generate, without a power supply.

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The second family of digital ICs will operate over a range of voltages (typically, a 9 V battery does the job exceedingly well), but are a little more easily damaged. Nevertheless, handled carefully and correctly, both families work well.

7400 series

The 7400 series of digital ICs is the variety that requires a fixed 5 V power supply. While there are many, many devices in the family only a few are of interest here. Before I explain about the ICs in detail though, a brief word about the 7400 series numbering.

The first two digits of any device in the family (that is, 74--) indicate that the device is a member of the family. The 7400 series is a family of digital ICs known as transistor–transistor logic (TTL) devices. The last two (or sometimes three) digits (--00) indicate which IC this is in the family. In other words a 7400 (which happens to be an IC with four, two input NAND gates) is different to a 7402 (which has four, two-input NOR gates).

A selection of ICs in the 7400 series is shown in Figure 11.1. Note that those shown — as I’ve already said — represent only a small fraction of the complete family.

Figure 11.1̃ Some integrated circuits from the 74 series of transistor–transistor logic (TTL) digital devices

4000 series

Like the 7400 series, the devices in the 4000 series are represented by their numbers. Note, though that the numbers between the two families do not correspond — in other words, a 4001 does not contain the same logic gates as a 7401.

A small part of the 4000 series is shown in Figure 11.2.

Figure 11.2 Some common devices from the 4000 series of digital integrated circuits — note that these cannot be directly interchanged with devices from the 74 series of TTL digital integrated circuits

Once we have a family (well, two families actually) of digital integrated circuits that contain logic gates, it’s fairly obvious that building more complex digital circuits becomes easier. It is merely a matter of using the gates within these integrated circuits to build more complex circuits. On the other hand, further devices in both ranges of integrated circuits are themselves more complex, containing circuits built from the gates themselves.

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