I understand the traditional difference between the 7400 series and the 4000 series logic ICs, but since there are CMOS versions of the 7400 series, is there an advantage to use the 7400 CMOS version over the 4000 series chips? Please note I'm not talking about TTL vs CMOS, as that has been discussed thoroughly before. If there is no difference (read significant difference), I'm assuming then that they would be able to interface with each other? I would think the voltage levels for high and low for both CMOS versions would be near identical, but please correct me if I'm wrong.

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    \$\begingroup\$ For a start, compare the propagation delay specs for any of the 74xx00 CMOS types to 4000-series. I just checked quad 2-input NAND gates (CD4011B and 74LVC00A) and the improvement is 10x. \$\endgroup\$
    – The Photon
    Commented Mar 16, 2016 at 21:36
  • \$\begingroup\$ You're saying that the 7400 series is retaining the characteristics of the TTL speeds (or near I suppose), but simply implemented with CMOS technology? As in the 7400s are faster than 4000s? \$\endgroup\$
    – bit0fun
    Commented Mar 16, 2016 at 21:37
  • \$\begingroup\$ The LVC's are much faster than the CD4000's. If you want to check the others, you'll have to download the datasheets yourself. \$\endgroup\$
    – The Photon
    Commented Mar 16, 2016 at 21:40
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    \$\begingroup\$ As I did not see this mentioned in the answers: For a comparison per family, have a look at this Wikipedia page: en.wikipedia.org/wiki/Logic_family You need to scroll down a bit to see a nice table. \$\endgroup\$ Commented Mar 16, 2016 at 21:56
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    \$\begingroup\$ @bit0fun: there are several 74xx CMOS families: C, HC, AC, LVC,... with huge differences among them. Which one do you want to compare to 4000 CMOS? \$\endgroup\$
    – Curd
    Commented Oct 13, 2017 at 9:51

2 Answers 2


The difference depends on your system definition. On the one hand, 74HC operates over a limited voltage range, with 6 volts specified as the maximum supply voltage. The CD4000 series, on the other hand, is rated to a maximum of 18 volts, so it may well be easier to use the CD4000 series in a battery-operated system.

If the limited voltage range of the 74HC line is not a problem, the line is much faster. For instance, comparing the CD4011/74HC00 (Quad 2-input NAND gates) gives propagation delays at 5 volts of 90 nsec (typ) vs 7 nsec. For the CD4063 vs the 74HC85 (4-bit magnitude comparator) the numbers are 625 nsec (typ) vs. 63 nsec. The CD40192 4-bit up/down counter has a typical count frequency of 4 MHz, while the 74HC192 goes at 36 MHz.

It's worth keeping in mind that both lines run faster at higher Vdd, so a CD4000 at 15 volts will do better than the numbers here, but the order of magnitude difference is not erased.

And yes, the 74HC series is designed to roughly maintain the speeds of the 7400/74LS00 lines, and often allows drop-in replacement for much lower power.

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    \$\begingroup\$ There is/was also the 74Cxx (without the H) line and that one is/was comparable to 4000. All the other more advanced 74xx lines (HC, ACT, LVC, etc.) are of course faster. \$\endgroup\$
    – Curd
    Commented Oct 13, 2017 at 9:43
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    \$\begingroup\$ 74HC is definitely not a suitable drop in replacement for 74LS. That's what 74HCT is for. \$\endgroup\$
    – Curd
    Commented Oct 13, 2017 at 9:59

HC7400 runs 2v to 6v supplies (partly TTL compatible)
HCT7400 (fully TTL compatible) runs 5v +/- 0.5v supplies
4000 series runs 3v to 15v (recommended VDD)

so with 5v supply, 4000, HCT7400 and HC7400 are fully compatible

7400 is comparable speed to TTL
4000 is significantly slower


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