Write a short notes on (any two): a) PLA, b) Multiplexer c) V-F converter d) Encoder

Introduction

In digital circuit design, various components are used to perform specific functions. These components include Programmable Logic Array (PLA), Multiplexer, Voltage-to-Frequency converter (V-F converter), and Encoder. Each of these components has a unique structure and function, and they are used in various applications in digital circuits.

PLA (Programmable Logic Array)

Definition and Purpose

A Programmable Logic Array (PLA) is a type of digital logic device that can be programmed to implement complex logic functions. It is a kind of programmable logic device used to implement combinational logic circuits.

Structure

A PLA consists of three main parts: a set of programmable AND gates, a set of programmable OR gates, and programmable links that connect the AND and OR gates. The AND gates generate all the possible combinations of the inputs, and the OR gates combine these combinations to produce the desired output.

Working

In a PLA, the AND gates are used to generate all the possible combinations of the input variables. These combinations are then fed into the OR gates, which combine them to produce the desired output. The programmable links are used to determine which combinations are used in the OR gates.

Example

For example, consider a simple logic function F = A.B + C. This function can be implemented using a PLA with two AND gates and one OR gate. The first AND gate is programmed to generate the product A.B, and the second AND gate is programmed to generate C. The OR gate is then programmed to combine these two outputs to produce F.

Advantages and Disadvantages

The main advantage of a PLA is its flexibility. It can be programmed to implement any combinational logic function. However, the main disadvantage of a PLA is its complexity. It requires a large number of gates and programmable links, which can make it difficult to design and manufacture.

Multiplexer

Definition and Purpose

A multiplexer, also known as a mux, is a combinational circuit that selects binary information from one of many input lines and directs it to a single output line. The selection of a particular input line is controlled by a set of selection lines.

Structure

A multiplexer consists of multiple input lines, one output line, and multiple select lines. The number of select lines determines the number of input lines. For example, a 4-to-1 multiplexer has 4 input lines, 1 output line, and 2 select lines.

Working

The select lines of a multiplexer determine which input to send to the output. If the select lines are set to a particular binary value, the corresponding input line is connected to the output.

Example

For example, in a 4-to-1 multiplexer with input lines I0, I1, I2, and I3, if the select lines S1 and S0 are set to 00, then I0 is selected and sent to the output. If S1 and S0 are set to 01, then I1 is selected, and so on.

Advantages and Disadvantages

The main advantage of a multiplexer is its ability to handle multiple inputs and direct them to a single output, which can simplify circuit design. However, the main disadvantage is that only one input can be selected at a time, which can limit its use in certain applications.

Conclusion

PLA and Multiplexer are vital components in digital circuit design. They are used to implement complex logic functions and manage multiple inputs, respectively. Understanding their structure, function, and advantages and disadvantages is crucial for effective digital circuit design.

Summary

This notes provides an introduction to PLA and Multiplexer, explaining their structure, working, examples, advantages, and disadvantages.

Analogy

Think of a PLA as a customizable puzzle where you can choose the pieces (AND gates and OR gates) to create any desired logic function. On the other hand, a multiplexer can be compared to a traffic signal that directs one car (input) at a time to the main road (output) based on the selected route (select lines).