The document explains logic families in digital integrated circuits, which are classified by their technology and include types like TTL, CMOS, and ECL. It details characteristics of ideal logic families, such as low power and high speed, along with concepts of fan-in, fan-out, and propagation delay that are crucial for circuit functionality. The document also highlights that older families like diode logic and resistor transistor logic are now obsolete, while TTL, CMOS, and ECL are still widely used.

1. Logic Families
Name : Yaksh Jethva
yakshjethva_123@yahoo.com

2. Content
Logic family
->What is logic family ?
->Different type of logic families
About FANIN and FANOUT
About propagation delay

3. Logic family
Digital integrated circuits are classified not only by their complexity or
logical operation,but also by the specific circuit technology to which
they belong. The circuit technology is referred to as a digital logic
family.
Each logic family has its own basic electronic circuit upon which more
complex digital circuits and components are developed. The basic circuit
in each technology is a NAND, NOR, or inverter gate.

4. Types of Logic families
The digital ICs are designed using any of either bipolar devices or MOS or a combination of both.
Bipolar families, this include diode logic (DL), emitted coupled logic (ECL), resistor transistor logic (RTL), diode
transistor logic (DTL), transistor transistor logic (TTL).
MOS family are PMOS, NMOS family, CMOS family. Bi-MOS logic family is the one that uses both bipolar and
MOS devices.
Of the above mentioned families DL, RTL and DTL are not used these days they have become obsolete. TTL,
CMOS, ECL, NMOS and Bi-CMOS are the families which are still used.
Many different logic families of digital integrated circuits have been introduced commercially. The following are
the most popular:
TTL transistor–transistor logic;
ECL emitter‐coupled logic;
MOS metal‐oxide semiconductor;
CMOS complementary metal‐oxide semiconductor.

5. Characteristics of ideal logic family
The ideal logic family should have or be:
➔ Low power
➔ High speed
➔ Easy to use
➔ Many different logic function

6. TTL(Transistor Transistor Logic)
➔ TTL are only build around the transistor.
➔ TTL is developed in 1965.
➔ Through the years basic TTL has been improved to meet performance
requirements.
Types of TTL:
● Standard TTL
● High speed TTL
● Low power TTL

7. CMOS Logic

8. About FANIN and FANOUT
Fan In: The fan-in defined as the maximum number of inputs that a logic gate can accept.
If number of input exceeds, the output will be undefined or incorrect. It is specified by
manufacturer and is provided in the data sheet.
Fan Out: The fan-out is defined as the maximum number of inputs (load) that can be
connected to the output of a gate without degrading the normal operation.

9. Propagation Delay
Propagation delay is the time required for a digital signal to travel from the
input(s) of a logic gate to the output.
Propagation delay symbolized with tpd.
It is measured in microseconds (µs),nanoseconds (ns), or picoseconds (ps).
Propagation delay is important because it has a direct effect on the speed at
which a digital device, such as a computer, can operate. This is true of memory
chips as well as microprocessors.

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