Digital IC Family. Digital IC Introduction Digital ICs are more reliable by reducing the number of...
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Transcript of Digital IC Family. Digital IC Introduction Digital ICs are more reliable by reducing the number of...
Introduction
• Digital ICs are more reliable by reducing the
number of external interconnections from one
device to another.
• Before ICs, every circuit connection was from
one discrete component to another.
Cont.,
• A logic family refers to digital integrated
circuit devices which are constructed with
a combination of electronic gates.
• A family has its own power supply voltage
and distinct logic levels.
Cont.,
• Each family has its own characteristics,
advantages and disadvantages.
• Also within each family, there is a range of
voltages which may be high level or low level.
Cont.,
• The various logic families can be placed into
two brand categories according to the IC
fabrication process.
• Bipolar
• Metal-oxide semiconductor (MOS)
Bipolar Logic families
• The important elements of a bipolar IC are
resistors, transistors and diodes.
• Based on the two main operations of bipolar ICs,
i.e.,
• Saturated
• Non-saturated.
Saturated bipolar Logic families
• Resistor-Transistor Logic (RTL)
• Direct-Coupled Transistor Logic (DCTL)
• Diode-Transistor Logic (DTL)
• High Threshold Logic (HTL)
• Transistor-Transistor Logic (TTL)
• Integrated-Injection Logic (IIL)
Metal Oxide Semiconductor (MOS)
The MOS families include
• PMOS p-channel MOSFETs
• NMOS n-channel MOSFETs
• CMOS Complementary MOSFETs
Speed of operation
• The speed of operation of an IC is expressed in
terms of propagation delay.
• Propagation delay is defined as the time taken
for the output of a gate to change after the
inputs have changed
Cont.,
• The time difference between the application of
input and appearance of output is also called
as propagation delay.
Power dissipation
• Power dissipation is the nature of the power
consumed by a logic gate when fully driven by
all its inputs.
• It is expressed in mill watts or nano watts
Fan in
• The fan-in of a gate is the number of inputs
connected to the gate without degradation in
the voltage levels.
Fan out
• Fan out is the maximum number of similar
logic gates that a gate can drive without any
degradation in voltage levels.
Noise immunity
• The noise immunity of a logic circuit refers to
the circuit ability to tolerate noise without
causing spurious changes in the output voltage.
• A quantitative measure of the noise immunity is
called noise margin.
Operating Temperature
• ALL IC gates are semiconductor devices that are
temperature-sensitive by nature.
• The operating temperature ranges for and IC
vary from 00 C to +700 C for consumer and
industrial applications and from -550 C to + 1250
C for military applications
Power supply requirements
• The amount of power and supply voltage
required by an IC are the main parameters to
be taken into consideration while choosing a
proper power supply