# What is 74LS138 decoder?

## What is 74LS138 decoder?

74LS138 is a complex TTL based logical device used to convert 3-bit binary data to 8-bits. The actual purpose of this chip is designed for demultiplexing or in machine language we can say as a decoding device. The device takes 3 input data and converts it to 8-bit data.

### How many decoders are there in 74LS138?

74LS138 is a member from ’74xx’family of TTL logic gates. The chip is designed for decoding or de-multiplexing applications and comes with 3 inputs to 8 output setup.

#### What is the use of IC 74LS138?

Use of 74138 to generate chip select logic: 74138 is used to generate chip signals.

**Which output of 74LS138 decoder will be activated if a 1 B 0 and C 1?**

When the input of the adder is: a=1, b=0, ci=1, the input of the corresponding 3-line to 8-line decoder is A=1, B=0, C=1. The output of the decoder is out (5) = 1 and the rest is 0. According to the connection relationship designed above, S = 0, CO = 1, which satisfies the function of full adder.

**What is a 3 to 8 decoder?**

3 to 8 line decoder: The 3 to 8 line decoder is also known as Binary to Octal Decoder. In a 3 to 8 line decoder, there is a total of eight outputs, i.e., Y0, Y1, Y2, Y3, Y4, Y5, Y6, and Y7 and three outputs, i.e., A0, A1, and A2. This circuit has an enable input ‘E’.

## What is difference between decoder and demux?

A Decoder decodes an encrypted input signal to multiple output signals from one format to another format. A De-Multiplexer routes an input signal to multiple output signals. A Decoder has ‘n’ input lines and maximum of 2n output lines. A De-Multiplexer has single input, ‘n’ selection lines and maximum of 2n outputs.

### What is 74LS138 IC?

The IC 74LS138 is a 3 to 8 line decoder integrated circuit from the 74xx family. The main function of this IC is to decode otherwise demultiplex the applications. The decoder 74LS138 IC uses advanced technology like silicon (Si) gate TTL technology. 74LS138 IC has 3 binary select inputs like A, B & C.

#### What is a IC decoder?

Decoders are digital ICs which are used for decoding. In other words, the decoders decrypt or obtain the actual data from the received code, i.e. convert the binary input at its input to a form, which is reflected at its output. It consists of n input lines and 2^n output lines.

**How is decoder size calculated?**

Decoder is used to convert binary to other codes. Such as, binary to octal, binary to hexa decimal and BCD to decimal. The size of the decode is N×2N. Therefore, for given problem size of the decoder is 5 × 32.

**How many 2×4 decoders are needed for 4×16?**

Update: you need 5 decoders.

## How many outputs can a 3/8 decoder make?

eight outputs

In 3 to 8 line decoder, it includes three inputs and eight outputs. Here the inputs are represented through A, B & C whereas the outputs are represented through D0, D1, D2… D7.

### Is demux and encoder same?

Characteristic of Decoder and a Demultiplexer – A decoder takes n input lines and produces 2^n output lines, unlike an encoder which takes 2^n input lines and produces n output lines. A Demultiplexer transmits data from one line to 2^n possible output lines, where the output line is determined by n select lines.

#### Can you call a decoder as a Demux?

A decoder with an enable input can function as a Demultiplexer. A demultiplexer is a circuit that receives information on a single line and transmits this information on one of 2n possible output lines.

**How many types of decoders are there?**

There are different types of decoders like 4, 8, and 16 decoders and the truth table of decoder depends upon a particular decoder chosen by the user. The subsequent description is about a 4-bit decoder and its truth table.

**How do I know how many RAM chips I need?**

To design a RAM size of 512×8 from 128×8, here are some calculations we need to do first:

- Number of chips required: Number of chips required = Desired RAM Size/ Basic RAM Size =512×8/128×8 =4 chips.
- Address Bits: Required Size is 512 x 8 512 x 8= 29 x 8 Therefore, 9 bit address is required.

## What is a 2 4 decoder?

The 2-to-4 line binary decoder depicted above consists of an array of four AND gates. The 2 binary inputs labelled A and B are decoded into one of 4 outputs, hence the description of 2-to-4 binary decoder. Each output represents one of the minterms of the 2 input variables, (each output = a minterm).

### How do I know which decoder to use?

How to choose a locomotive decoder (incl. cheat sheet)

- Step 1: Choose a compatible protocol. The most important step: make sure the locomotive decoder speaks the same language as your command station.
- Step 2: Choose the right digital interface.
- Step 3: Check available space.
- Step 4: Check decoder specs.

#### How can I make 4X16 decoder using 2X4?

Basically start with 2 of the 6 inputs for the 2X4 decoder. The 4 outputs will drive the enable pin of the four 4X16. And the remaining 4 of the 6 inputs will be the 4 inputs for all four 4X16. This way, the 2X4 select which 4X16 to turn on; and the remaining addresses picks 1 of the 16 outputs.

**How many 3×8 decoders are needed for 4×16 decoder?**

A decoder circuit of the higher combination is obtained by adding two or more lower combinational circuits. 4 to 16 decoder circuit is obtained from two 3 to 8 decoder circuits or three 2 to 4 decoder circuits. When two 3 to 8 Decoder circuits are combined the enable pin acts as the input for both the decoders.

**What is the difference between Mux & Demux?**

Multiplexer refers to a type of combinational circuit that accepts multiple inputs of data but provides only a single output. The demultiplexer refers to the type of combinational circuit that accepts just a single input but directs it through multiple outputs. A Multiplexer performs conversion from parallel to serial.

## What is the difference between a demux and decoder?

### Which memory is fastest?

Cache memory is the fastest system memory, required to keep up with the CPU as it fetches and executes instructions. The data most frequently used by the CPU is stored in cache memory.

#### How many chips are needed to make 4K bytes?

Therefore 4*8 = 32.

**What is a 2 function DCC decoder?**

Dcc Dual Function Decoder with Transponder supports 2 function outputs as well as transporting, great for adding lighting features to your rolling stock. Retired in 2003. TF2 Features: Two 125mA function outputs for lights or other functions (Peak rating is 250mA) Each function output can be operated independently.