Importance, Types, and Characteristics of Logic Families

Logic Families are defined as a group of electronic logic gates and circuits used in IC (Integrated Circuits). Characteristics of Logic Families are Speed, Fan-in, Fan-out, Noise Immunity, Power Dissipation. Types of Logic Families in Digital Electronics are TTL, CMOS (Complementary Metal-oxide Semiconductor), ECL, RTL, DTL. In this article, we will see the importance, types, and characteristics of logic families in detail.  

Characteristics of Logic Families

Main Characteristics of Logic Families are – Speed, Fan-in, Fan-out, Noise Immunity, and Power Dissipation.

Let us see all the characteristics in greater detail.

  • Speed – Speed is decided by observing the time span between applying the input to the given circuitry and change in output.
  • Fan – in – This characteristic of logic is one of the most important because it decides how much input a logic circuit would be able to handle.
  • Fan – out – This is something similar to Fan – in except it decides how much circuits a particular gate would be able to drive.
  • Noise Immunity – Noise immunity is self-explanatory. It will tell you how much noise any circuit can handle without breaking the output.
  • Power Dissipation in CMOS – Any given circuit, when switches to another state from one state, there is some power dissipated. That is known as Power Dissipation in CMOS.

characteristics of logic families

Logic Families refer to the type of logic circuit in the chips. Usage of different circuit configurations and production technologies takes place during the creation of digital integrated circuits. Any such approach can be described as Logic Families. Furthermore, when the fabrication of each and every chip of a particular logic family takes place, the ICs will have identical electrical characteristics. CMOS logic family happens to be one of the most popular logic families.

Importance of Logic Families in Digital Electronics

First of all, digital ICs make up the whole digital system. In case the ICs belong to the same logic family then there will certainly be compatibility among them. This ensures the performance of the intention driven logic functions. Consequently, the goal is achieved.

Another situation can be the one in which the use of ICs of different logic families takes place. In such a case, the use of interfacing techniques must take place in order to ensure compatibility.

Most noteworthy, this shows the need to acquire an understanding of the different logic families. Furthermore, this understanding would lead to the best combination of ICs during the design of a digital system.

Types of Logic Families

The design of the digital ICs takes place by making use of bipolar devices or MOS or both. The first kind of logic families is bipolar families.

The families included here comprise of Emitted coupled logic (ECL), resistor transistor logic (RTL), diode transistor logic (DTL), transistor logic (TTL), and diode logic (DL).

The other logic family is the MOS family and this includes NMOS, PMOS, and CMOS family. Moreover, a family whose name is Bi-MOS family makes use of both bipolar and MOS devices.

Learn more about Master-Slave JK Flip Flop to understand this concept in more detail.

What is CMOS?

CMOS stands for complementary metal-oxide-semiconductor (CMOS). Furthermore, this particular technology is essential for the creation of digital circuitry. CMOS is a type of MOSFET fabrication process.

MOSFET stands for metal–oxide–semiconductor field-effect transistor. Moreover, the building blocks of CMOS circuits happen to be P-type and N-type MOSFET transistors. This particular technology is crucial in the construction of integrated circuits (IC) chips. Also, it is vital for analog circuits including RF circuits, data converters, and image sensors.

CMOS – Complementary Metal-Oxide Semiconductor

CMOS happens to be both a particular style of digital circuitry design as well as a family of processes that implement that particular digital circuitry style on integrated circuits.

There is the dissipation of lesser power with CMOS circuitry in comparison to the logic families with resistive loads. Consequently, CMOS processes and variants have significantly grown in importance and have come to dominate other logic families.

CMOS circuits make use of a combination of p-type and n-type MOSFETs for the implementation of logic gates and other digital circuits. The implementation of CMOS logic can take place with discrete devices.

Furthermore, commercial CMOS products are circuits and they comprise billions of transistors. Most noteworthy, CMOS always makes use of enhancement-mode MOSFETs.

Subfamilies of CMOS

The division of the subfamilies of CMOS is on the basis of the voltage difference and other parameters.

Most noteworthy, the subfamilies include 4000A, 4000B, 4000UB, 54/74C, 54/74HC, 54/74HCT, 54/74AC and 54/74ACT. The replacement of the 4000A subfamily has taken place by high-voltage versions in the 4000B AND 4000UB subfamilies.

The subfamilies 54/74C, 54/74HC, 54/74HCT, 54/74AC and 54/74ACT consist of TTL series logic functions which are pin-compatible 54/74.

Logic families mean the type of logic circuits in the IC. Furthermore, understanding of logic families helps in deriving the best combination of ICs. CMOS is a type of logic family among the various types available. It is important for the creation of digital circuitry.

Furthermore, it is a particular style of digital circuitry. Moreover, it is also a family of processes that implements digital circuitry style on integrated circuits. Also, CMOS has eight subfamilies.

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