4000 Series CMOS Parts?

Tony Duell wrote: Yes. 4000B series are rated for operation at from 3Vto 18V (abs max 20V), while 74HC series are rated for operation from 2V to 6V (abs max 7V). Also 4000B are generally *much* slower (at same voltage) than 74HCxxx parts. For instance, CD4011 prop delay at 5V and 25C is rated 125ns typ, 250ns max, while 74HC00 at 4.5V and 25C is rated 9 ns typ and 18ns max. Each family still has applications where it can't be replaced by the other, which is why (some parts of) both families are still in production. Nowadays my favorite 74xx families are 74ABT and 74LVC. The 74ABT family is great for buffers that need high output drive. The 74LVC family runs on 3.3V but has 5V-tolerant inputs, with low input leakage even when Vdd=0V. I wish there were more 74LVC parts offered in DIP packages for ease of prototyping, but DIP is going the way of the dodo. Ces't la vie. At least the 74LVC240, '245, '373/573, and '374/574 are offered in DIP. I use those when I have to interface 5V inputs to a 3.3V I/O system (i.e., FPGA, microcontroller) that does not have 5V-tolerant I/O. In the other direction, 3.3V CMOS outputs can directly drive 5V chips that have TTL-compatible inputs, but when it is necessary to drive 5V parts that actually expect 5V CMOS input levels, the 74HCT, 74ACT, or 74ABT series is useful.