74 Family Series Meaning of Lettering
The 74xx series of integrated circuits (IC), also known as monolithic IC, use very specific meanings for their letter designations. The lettering scheme provides engineers with a quick means to determine their compatibility with any project circuit. As semiconductor technology improved, manufacturers improved the IC, and consequently, many of the older integrated circuits are no longer available. Hence, the good news is that you will not have to be familiar will all the letterings.
| Family | Input | Output | Technology | Vcc |
| TTL | TTL | TTL | Bipolar | 5 V |
| S | TTL | TTL | Bipolar | |
| LS | TTL | TTL | Bipolar | |
| ALS | TTL | TTL | Bipolar | |
| AS | TTL | TTL | Bipolar | |
| HCT | TTL | CMOS | CMOS | |
| HC | CMOS | CMOS | CMOS | |
| BCT | TTL | TTL | BiCMOS | |
| 74F | TTL | TTL | Bipolar | |
| ACT | TTL | CMOS | CMOS | |
| AC | CMOS | CMOS | CMOS | |
| AHCT | TTL | CMOS | CMOS | |
| AHC | CMOS | CMOS | CMOS | |
| ABT | TTL | TTL | BiCMOS | |
| FCT | TTL | TTL | BiCMOS | |
| LV | LVTTL | LVTTL | CMOS | 3.3 V |
| AHC | CMOS | CMOS | CMOS | |
| AC | CMOS | CMOS | CMOS | |
| ALB | LVTTL | LVTTL | BiCMOS | |
| LVC | LVTTL | LVTTL | CMOS | |
| ALVC | LVTTL | LVTTL | CMOS | |
| LVT | LVTTL | LVTTL | BiCMOS | |
| ALVT | CMOS | LVTTL | BiCMOS |
This chart shows two main divisions based on operating voltage. Those integrated circuits based on CMOS technology will operate at 3.3 V; however, there are some, which will operate at 5 V as well. For example, the "AC" version will operate at both 3.3 V and 5 V and still provide CMOS compatible outputs.
Operating Voltage Range (Vcc)
| 74 Series | Vcc |
| 74AHCT1G | 4.5 - 5.5 |
| 74AHC2GxxH | 2.0 - 5.5 |
| 74AHC1GxxH | 2.0 - 5.5 |
| 74AHC1G | 2.0 - 5.5 |
| 74LVC1G/2G/3G | 1.65 - 5.5 |
| 74AUC1G/2G/3G | 0.8 - 2.7 |
| 74AVC | 1.4 - 3.6 |
| 74ALVT | 2.3 - 3.6 |
| 74ALVC | 1.65 - 3.6 |
| 74LVT | 2.7 - 3.6 |
| 74LVC | 2.0 - 3.6 |
| 74LV | 2.0 - 5.5 |
| 74HC | 2.0 - 6.0 |
| 74AHC | 2.0 - 5.5 |
| 74AC11 | 2.0 - 5.5 |
| 74AC | 2.0 - 5.5 |
| 74LS | 4.75 - 5.25 |
| 74S | 4.75 - 5.25 |
| 74xx (Standard) | 4.75 - 5.25 |
| 74BCT | 4.5 - 5.5 |
| 74F | 4.5 - 5.5 |
| 74ALS | 4.5 - 5.5 |
| 74AS | 4.5 - 5.5 |
| 74ABT | 4.5 - 5.5 |
This chart shows the operating voltage range of the integrated circuits. It is interesting to note that the low voltage (LV) chips will operate at extremely low voltages down to 0.8 V, 1.65 V, and 2 V.
Letters and Meanings
| Letters | Meaning |
| A | Advanced |
| S | Schottky |
| L | Low Power |
| B | BiCMOS |
| T | TTL |
| C | CMOS |
| F | Fast |
| H | High Speed |
| 1G | First Generation |
| 2G | Second Generation |
| 3G | Third Generation |
| Q | Quiet Outputs |
| V | Voltage |
| P | Power |
Examples
For example if you had a SN74AC244: The letters indicates that this is an AC family of chips -- Advanced CMOS -- based on CMOS technology. It can operate at 5 V. The same series listed in the 3.3 V categories uses less power and voltage. For either of the voltages the chip expects a CMOS level input and provides a CMOS level output.
- TTL - Transistor Transistor Logic
- HTTL - High Speed TTL
- LPTTL - Low Power TTL
- STTL - Schottky TTL
- LSTTL - Low Power Schottky TTL
History
The 7400 family of integrated circuits was huge at one time and in the order of thousands. Besides logic gates, there was an IC for almost every function such as, line drivers, registers, exotic counters, and processors. Many of the early Intel microprocessors consisted of discrete integrated circuits hence there were adders, and registers, and bus controllers. However today, many of these are obsolete. Apart from the very basic logic gates, and counters, many ICs are unobtainable today.
With my anorak on, I usually travel the world in search of a vintage chip, and I have the complete collection of vintage monolithic ICs, including some of the early vintage ones by Texas Instruments, and Fairchild Semiconductors. Motorola joined shortly afterwards, and I have the complete collection of their chips as well. I am missing only 22 chips from the 60s period and those chips were manufactured by TI for NASA for the Apollo guidance computer.