What does Linear in electronic mean?

Hi everyone,

In electronics what does linear mean?

What is the most simplest definition of linear? Its a word that has been bugging me for years :biggrin:

Comes as sometimes Linear circuit, or output current is linear etc.

What is the opposite of linear?

Many thanks.

Reply 1

Stonebridge

Original post by Mo-Student

Hi everyone,

In electronics what does linear mean?

What is the most simplest definition of linear? Its a word that has been bugging me for years :biggrin:

Comes as sometimes Linear circuit, or output current is linear etc.

What is the opposite of linear?

Many thanks.

It applies to a system where the output varies continuously as a function of the input.
You could also use the word "analogue" here.

The opposite, then, would be "digital".

In physics, linear has a lot of different applications and shades of meaning.

Reply 2

Mo-Student

Original post by Stonebridge

Thanks so an output which changes continuously for example 2V then 4V, 3V, 5V etc? where as the input stays put with a fixed value of say 10v?

Thank you, you made me finally understand it

My physics only the electrical and electronic side only

Reply 3

Stonebridge

Original post by Mo-Student

Thanks so an output which changes continuously for example 2V then 4V, 3V, 5V etc? where as the input stays put with a fixed value of say 10v?

Thank you, you made me finally understand it

My physics only the electrical and electronic side only

No. No.

If the input changes smoothly from say 2V to 4V and the output changes smoothly as a result from 10V to 20V that is "linear". The output = 5 x input. It varies as a function of the input.

If the input was rising smoothly from 2V to 4V and the output suddenly changed from 5V to 20V at some point in between that would not be linear.

Reply 4

Mo-Student

Original post by Stonebridge

Ok so as you said the output needs to 5x the input, is this 5x input a must condition for it be considered linear? Can it be 10x input or 2x input etc why 5x is this the rules set which cannot be disputed? Because transformers can step-up the voltage greater than 5x the input.

The other thing is as I can see you said that the output has to be greater than the input. So now say any set-up circuits are the only circuits considered being linear circuits? Or they are the most deserving of being called "linear"?
As for example a set-up transformer circuit for AC Load, or a DC-DC step-up chopper circuits are both types of linear circuits?

Step-down transformer or DC-DC step-down choppers what are they called because they are the completely opposite to the step-up system.

Thanks for your help sir :smile:

(edited 8 years ago)

Reply 5

uberteknik

Original post by Mo-Student

Think of linear electronics as a collection of components performing a transfer function which acts to produce and manipulate continuously varying waveforms exclusively in the time-domain. It does not matter what the transfer function is, simply that the function is executed purely in the time domain in an analogue form: be that amplification, logarithmic, exponential, integration, differentiation, chopping, step-up, step down etc.

A digital circuit changes the execution domain of the transfer function from continuous time, to discrete time. i.e. discrete time divisions in which the binary numerical equivalent of the original waveform is created (A/D conversion) and manipulated in binary algebraic computational form before conversion and output to the continuous time domain (D/A conversion) once again.

All semiconductors and components, stand-alone as linear devices. They become part of a digital circuit as soon as the change from continuous time to discrete time is made.

Hence an A/D or D/A convertor will have both analogue and digital sub-functions. These devices are considered part linear and part digital and hence interfacing between the analogue and digital domains.

DC-DC convertors are not considered digital because they are power transfer devices and use waveform chopping as a method of significantly reducing the size of the analogue power transformers which are still needed nonetheless.

(edited 8 years ago)

Reply 6

Stonebridge

Original post by Mo-Student

5x was just one example of a circuit where the output depends smoothly on the input.
The output can be any continuously varying function.
I didn't say the output "had to be greater than" the input.
The output can be greater or less. It can even be the same.
Also read uberteknik's reply.