The list of packaged building-block logic families can be divided into categories, listed here in roughly chronological order of introduction, along with their usual abbreviations: The families (RTL, DTL, and ECL) were derived from the logic circuits used in early computers, originally implemented using discrete components.
The PMOS and I2L logic families were used for relatively short periods, mostly in special purpose custom large-scale integration circuits devices and are generally considered obsolete.
For example, early digital clocks or electronic calculators may have used one or more PMOS devices to provide most of the logic for the finished product.
Present-day "building block" logic gate ICs are based on the ECL, TTL, CMOS, and BiCMOS families.
Class of digital circuits built using resistors as the input network and bipolar junction transistors (BJTs) as switching devices.
A family of simple resistor–transistor logic integrated circuits was developed at Fairchild Semiconductor for the Apollo Guidance Computer in 1962.
A variant with integrated capacitors, RCTL, had increased speed, but lower immunity to noise than RTL.
These devices usually ran off a 15 volt power supply and were found in industrial control, where the high differential was intended to minimize the effect of noise.
ECL uses an overdriven bipolar junction transistor (BJT) differential amplifier with single-ended input and limited emitter current.
Variations on the basic TTL design are intended to reduce these effects and improve speed, power consumption, or both.
The introduction of Advanced Low-power Schottky (ALS) further increased speed and reduced power consumption.
CMOS logic gates use complementary arrangements of enhancement-mode N-channel and P-channel field effect transistor.
This means that the current draw of CMOS devices increases with switching rate (controlled by clock speed, typically).
VLSI technology incorporating millions of basic logic operations onto one chip, almost exclusively uses CMOS.
The extremely small capacitance of the on-chip wiring caused an increase in performance by several orders of magnitude.
On-chip clock rates as high as 4 GHz have become common, approximately 1000 times faster than the technology by 1970.
CMOS chips often work with a broader range of power supply voltages than other logic families.
This problem was solved by the invention of the 74HCT family of devices that uses CMOS technology but TTL input logic levels.
Propagation delay is the time taken for a two-input NAND gate to produce a result after a change of state at its inputs.
Values are very typical and would vary slightly depending on application conditions, manufacturer, temperature, and particular type of logic circuit.