This instructable will briefly explain the two logic families of IC's you will most likely be encountering and using in your circuit designs and how to ensure that the HIGH or LOW output of the other is translated and interpreted correctly between a TTL and CMOS device. This process is called voltage level shifting and is the subject of this instructable.
Turn the page and read up on the two logic families that you have probably already implemented in your designs.
Step 1: TTL Integrated Circuits
The bipolar logic family, as the TTL series falls under have had consideral improvements, the first being the 74H which provided twice the speed of the original 74xx series, but at a cost of over twice the power consumption. The next improvement was the74L which increased all the internal resistances, leading to a net improvement in power consumption, but increased the propagation delay.
A key improvement came with the 74S series which placed Schottky diodes across the base-to-collector junctions of the transistors. Capacitive effects were reduced and yielded a speed increase of a factor of 5 with about a two-times increase in power consumption. The above mentioned lines 74LSxx were derived from this series and reduced power consumption by about 1/3. The 74ALSxx improved performance even further. The 74F series, based on a new technology, reduced the propagation delays and even further reduced the size of the IC.