Hey readers! I hope you are doing great. Welcome to another article where we are discussing the integrated circuit device. Today, we’ll study the 74LS238 IC, which is a widely used component in different digital circuits as a multiplexer and demultiplexer. Multiple features of this IC, such as its low power performance and versatility, make it a good choice for electronic circuits.
In this article, you will see the basic introduction of 74LS238, the datasheet of this IC, its working principle, the simulation in Proteus, and its applications in detail. There is a lot of information to understand about this 3 to 8 line decoder and we’ll shed light on all these topics from scratch so let’s start working on it.
Figure 1: Basic structure of 74LS238 IC
It is designed to take three inputs in binary format only
The internal structure of this IC performs complex calculations of demultiplexing or decoding according to the circuit
On the output side, the inputs are converted into eight mutually exclusive outputs and the high value is only at one output
This IC is widely used in different digital circuits because of its versatility.
It has a reliable, simple, and straightforward working nature. Moreover, it is also preferred to convert complex circuits into simple ones because of their fine structure and the ability to fit in multiple types of circuits.
It has the feature of minimizing the effect of system decoding.
The details of the structure and functionalities of the 74LS238 IC can be understood from the details of its datasheet. Here are different points about this IC:
This IC has 16 pins that are packed in the dual inline package (DIP). Here is the diagram that describes its structure:
Figure 2: Pinout configuration of 74LS238
All the pin numbers have a specific name in alphanumeric format. The details of each pin and its description are given here:
Symbol |
Pin Number |
Description |
Active State |
A0 |
1 |
Address input |
- |
A1 |
2 |
Address input |
- |
A2 |
3 |
Address input |
- |
E1 |
4 |
Enable input |
LOW |
E2 |
5 |
Enable input |
LOW |
E3 |
6 |
Enable input |
HIGH |
Y0 |
7 |
Output |
HIGH |
Y1 |
9 |
Output |
HIGH |
Y2 |
10 |
Output |
HIGH |
Y3 |
11 |
Output |
HIGH |
Y4 |
12 |
Output |
HIGH |
Y5 |
13 |
Output |
HIGH |
Y6 |
14 |
Output |
HIGH |
Y7 |
15 |
Output |
HIGH |
GND |
8 |
Ground (0 V) |
- |
VCC |
16 |
Supply voltage |
- |
Table 1: Pinout configuration of 74LS238
The 74LS238 is used as the 3 to 8 line decoder. The binary combination of three inputs results in different outputs. Here is the detail in the form of the function table:
Enable Inputs |
Select Input |
Outputs |
|||||||||||
G1 |
G2A |
G2B |
C |
B |
A |
Y0 |
Y1 |
Y2 |
Y3 |
Y4 |
Y5 |
Y6 |
Y7 |
X |
H |
X |
X |
X |
X |
L |
L |
L |
L |
L |
L |
L |
L |
X |
X |
H |
X |
X |
X |
L |
L |
L |
L |
L |
L |
L |
L |
L |
X |
X |
X |
X |
X |
L |
L |
L |
L |
L |
L |
L |
L |
H |
L |
L |
L |
L |
L |
H |
L |
L |
L |
L |
L |
L |
L |
H |
L |
L |
L |
L |
H |
L |
H |
L |
L |
L |
L |
L |
L |
H |
L |
L |
L |
H |
L |
L |
L |
H |
L |
L |
L |
L |
L |
H |
L |
L |
L |
H |
H |
L |
L |
L |
H |
L |
L |
L |
L |
H |
L |
L |
H |
L |
L |
L |
L |
L |
L |
H |
L |
L |
L |
H |
L |
L |
H |
L |
H |
L |
L |
L |
L |
L |
H |
L |
L |
H |
L |
L |
H |
H |
L |
L |
L |
L |
L |
L |
L |
H |
L |
H |
L |
L |
H |
H |
H |
L |
L |
L |
L |
L |
L |
L |
H |
Table 2: Function table of 74LS238
The following are some other devices that have similar features and can be used in place of 74LS238:
74HC238
SN74HCT238
LS238C
TS74HC238P
We know that ICs are made of a combination of logic circuits. The internal structure of these ICs makes the concept of working of the IC clear. If you want to have the details of its structure, you can have a look at the logic diagram of 74LS238 in a positive state:
Figure 3: Logic diagram of 74LS238
If you want to learn this datasheet in detail, you can have a look at the linked article give here:
The basics of the working of this IC in detail are shared with you so that you may know the expected outcomes when using the 74LS238:
This IC consists of three inputs that take only binary information. It means the inputs are only in the form of 0 and 1. The combination of these numbers decodes the output line, where the signals will be high.
The decoding logic of the 74LS238 depends on the internal structure that varies from manufacturer to manufacturer. The logic diagram is shared with you in this tutorial. Different combinations of these logic gates are used to get the required output.
This IC usually consists of AND and NOT gates that process the inputs together and provide the expected output at the output.
The internal structure is responsible for setting one of the eight bits high. This is the basic expectation of this integrated circuit. After processing the input bits, only one output bit is selected where the HIGH signals are sent. All other bits remain low.
There are three enable pins (E1, E2, and E3) that work as the master switch of the decoder. The functionality of each of these is given next:
The E1 and E2 pins work closely with each other and if any one of these is HIGH, the output is always HIGH, no matter what the inputs are.
The pin E3 provides additional control over the output of the decoder. It is an important pin because it acts as the AND gate with three inputs and the overall output is HIGH only when the result of this AND gate combination is set to LOW.
If you want to check the working of this IC then a good option is the proteus simulation. Here, I have created a simple circuit of this IC that will help you understand how the output is generated with 74LS238:
Till now, I hope you have an idea of the working of this IC but I have created a table that clearly describes its features and specifications of 74LS238 at a glance:
Category |
Feature |
Description |
General Information |
Function |
3-to-8 line decoder with active LOW outputs |
Family |
TTL (Transistor-Transistor Logic) |
|
Logic Level |
Low-power Schottky (LS) |
|
Package Type |
DIP (Dual In-Line Package) with 16 pins |
|
Inputs |
A0, A1, A2 |
Binary address inputs (3 lines) |
E1, E2, E3 |
Enable inputs (3 lines, all must be LOW to enable outputs) |
|
Outputs |
Y0 to Y7 |
Active LOW decoded outputs (8 lines) |
Key Specifications |
Propagation Delay |
15 ns typical |
Power Dissipation |
19 mW typical |
|
Supply Voltage |
4.75 V to 5.25 V |
|
Operating Temperature |
0°C to 70°C |
Before designing the circuit with the 74LS328, it is crucial to know the dimensions of this IC. Here is the table that describes its exact size in metric and imperial units:
Dimension |
Value (mm) |
Value (inches) |
Width |
6.10 |
0.240 |
Length |
9.91 |
0.390 |
Height |
3.81 |
0.150 |
Lead Spacing |
2.54 |
0.100 |
The 3 to 8 line decoders have applications in multiple fields where the digital circuits are the basic devices. The main application of 74LS238 is in the form of a 3 to 8 line decoder and here are some examples of its applications:
In circuits like memory banks, an important process is to calculate the higher address bit. Here, the 74LS238 is widely used and its basic duty is to activate the most appropriate memory chip. In some cases, it also activates the specific memory location within that chip.
Some microcontrollers have limited input-output ports, therefore, ICs like 74LS238 are used to expand the availability of the pins by providing the decoding process. Through decoding, the microprocessor can successfully select the required device at a time.
In display devices where the output is created by stimulating the specific arrangement of the LEDs, the 74LS238 plays a crucial role. For instance, in the 7-segment display, 74LS238 can illuminate the particular segments. As a result, the output shows the particular digit.
The logic circuits consist of multiple logic gates and other related components. Logic gates are simple circuits and provide basic functionality but if the user wants to have a higher level of performance, there is a need for complex circuitry that is difficult to understand. The 74LS238 has built-in decoding functionalities therefore, using this IC in the logic circuit is a good idea to reduce the complexities of the circuit.
In this way, we have understood the basic information of the 74LS238 in detail. In this article, we have started from the scratch and learned about the introduction of the 74LS238 in detail. We saw the datasheet of this IC and understood the basic features in detail. We also created the simulation of 74LS238 in Porteus and in the end, we saw the physical dimensions and applications of this decoder. I hope this was a useful study for you and if you want to add more authentic information to it, you can contact us.
Hello, peep! I hope you are doing great. Today, I’ll explain to you a very basic and interesting topic in the electrical world. We know printed circuit boards act as the backbone of complex circuits, and microwave PCBs are an important member of this family. These are the integral components of the high-frequency circuit designs. We will study microwave PCBs in detail and find out the perfect type of circuit where these are widely used.
Now, the question arises as to where the best PCBs can easily be ordered. It is crucial to get sensitive devices like printed circuit boards from the right vendor because quality is the first parameter to be considered in such shopping. One of the most reliable sources to get microwave PCBs without any difficulty is PCBWay Fabrication House. It is a popular manufacturer and seller of PCBs and their prototyping. The users can have low-volume production and a wide variety of PCB assembly services, all of which are available under one roof.
PCBWay is one of the largest manufacturers of PCBs and provides a great variety of PCBs and related components. They not only sell PCBs but also provide services such as manufacturing, designing, prototyping, and other processes. They have a large staff that helps the users to get their queries solved instantly. I suggest you visit PCBWay.com to get any services related to electronic circuit components, especially PCBs.
In this article, we’ll start learning the introduction to microwave PCBs through the basic definition. After that, we’ll understand the features in detail and see the basic applications in different sensitive domains of electronics to understand their scope. Here is the introduction of these PCBs.
Microwave printed circuit boards are a specialized category of PCBs that are designed to be operated according to the stringent requirements of high-frequency circuits. As the name suggests, the basic purpose of using these PCBs is to have the best performance at a higher level of frequency, even in microwaves where other PCBs do not provide the right performance. At such high frequencies, these PCBs show the best performance with minimal loss and distortion. This is the reason why these have applications in extraordinary fields such as aerospace, medical devices, etc.
The basic reason behind the best performance of this PCB is because of its design. From material selection to the fabrication process, these PCBs are designed to keep high frequency in mind. Hence, the nuances of the material are vital to achieving signal integrity with reliable output.
Microwave PCBs are different from traditional PCBs because they are designed for the extraordinary Understanding the features of microwave PCBs will help you a lot to know their basics and applications.
As mentioned before, the basic reason behind the robust performance of these PCBs is because of the material used in their production. These are made with specialized substrate materials that have low dielectric constants and low dissipation factors. Common materials used in their production are:
Polytetrafluoroethylene (PTFE)
FR-4 with PTFE
Ceramic-filled PTFE composites
Here, the basic material is PTFE, whereas FR- and ceramic-filed PTFE are its variants.
As compared to ordinary PCBs, microwave PCBs are employed with thicker copper layers. This not only reduces conductor loss but also contributes to better thermal management. For this, more material is required, and usually, the thickness of microwave PCBs is greater than that of many other types.
One of the most critical features of microwave PCBs is their impedance maintenance. They are designed in such a way that they prevent the phenomenon of signal reflection in microwave signals. Microstrip or stripline configurations are important techniques used during its design, and this ensures efficient power transfer from one point to another in the PCB.
An important feature of this PC is that, during the design process, great care is taken to isolate the component. This includes processes such as strategic component placement and optimized routing so that the circuit has minimal crosstalk.
Another reason why these PCBs provide the best signal integrity is the via design. The following table shows the via design options in the microwave PCBs:
Feature |
Through-hole Via |
Blind Via |
Buried Via |
Connection |
Extends through the entire PCB |
Connects an outer layer to one or more inner layers |
Connects inner layers without penetrating the outer layers |
Visibility |
Visible on both the top and bottom of the PCB |
Visible on one side of the PCB (typically the top) |
Not visible on either side of the PCB |
Manufacturing method |
Drilling through the entire PCB |
Drilling partway through the PCB, then plating the remaining portion |
Laser drilling or plating through micro vias |
Cost |
Less expensive |
More expensive than through-hole vias, less expensive than buried vias |
Most expensive |
Reliability |
Highly reliable |
Less reliable than through-hole vias, more reliable than buried vias |
Least reliable |
Applications |
High-current applications, high-density designs |
Applications where vias need to be hidden on one side of the PCB, such as for cosmetic reasons or to prevent EMI |
High-density designs, applications where vias need to be hidden on both sides of the PCB |
Another way to maintain the performance of these PCBs is to set the electromagnetic interference (EMI) and electromagnetic compatibility (EMC) compliance in the design. This helps a circuit to adhere to the regulation of electromagnetic standards so that every component in the circuit has the experience of the right EMI and EMC. This not only results in better circuit design but is useful in testing and validation.
As we have discussed so far in this article, microwave PCBs are a specialized type of PCB. these have applications in the areas where PCB tolerance and high sensitivity are required. Here are some major fields where these PCBs are used:
In areas like aerospace and defence, high-performance circuits are extensively used and reliability is an important factor of these circuits. Here, the microwave PCBs are considered one of the best choices. The two most critical applications are discussed below:
For military and aerospace applications, radar systems are the basic devices and these require accurate performance all the time. In these devices, microwave PCBs help to get precise and rapid signal processing.
The electronic warfare system circuity requires a base that may bear the high frequency easily. For such systems, the microwave PCBs are the best choice. As a result, these PCBs help to have the best performance.
The microwave PCBs are the integral base of the systems in the telecommunication fields. These systems are loaded with wireless communication devices and here, usually, the best frequency is in the form of microwaves. Therefore, most of the devices use microwave PCBs to get the best performance.
Communication with the satellite requires a high frequency to communicate through the distance. For this, reliable devices that can bear the high frequency without disturbing the output are required and this is possible with the microwave PCBs.
The sensitive areas like medical imaging devices where accuracy and precision are the life-saving parameters, are always the best pieces of equipment used and microspace PCBs are worth discussing as part of these devices. Here are some medical applications where these PCBs are used:
In medical imaging devices, accuracy is an important factor because of the limitations of the colours. Here, the base of these devices is the microwave PCBs, because ideally, these do not distort the output even at the high frequency. Two important applications in this regard are magnetic resonance imaging (MRI) and computed tomography (CT) scanners.
These PCBs have applications in radio frequency (RF) ablation systems, where they help the expert work on medical treatment with precise control.
In laboratories and scientific research departments where heavy calculations are required and the device runs continuously for a long time, it is better to use microwave PCBs because of their feature to bear high frequencies.
The research applications get the most benefit from these PCBs and can work with the best results from their long-term calculations.
The scope of microwave PCBs is not limited to these fields but is widely used in industrial automation, consumer electronics, etc.
So, in this article, we have understood the basics of microwave PCBs. We started with the basic introduction and understood the features to clarify the concepts. After that, we saw the applications of microwave PCBs in different sensitive areas where they are used because of their features like accuracy and precision. Moreover, in the beginning, we discussed how PCBWay is the best choice to buy microwave PCBs. I hope you liked the content, and if you want to know something more, you can contact me through the comment section.