# Generating Harmonics from Non-linear devices

Discussion in 'Homework Help' started by Energetic, Jan 10, 2011.

1. ### Energetic Thread Starter Member

Jan 3, 2011
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0
Hi,

I have to show two non linear devics generating harmonics in multisim. I have managed to acheive this with a diode for one but have not managed to replicate this with an inductor, transformer, or any other supposed harmonic generating non linear device.

I have tried various voltages, frequencies and circuits but no joy. Can anyone recommend a suitable component and at what frequency and voltage etc i will be able to see harmonics on my spectrum analyser.

Cheers ears...

Apr 5, 2008
15,645
2,344
Hello,

What about an amplifier that clips?
That will give a lot of distortion and harmonics.

Bertus

Energetic likes this.
3. ### Papabravo Expert

Feb 24, 2006
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Gee I thought inductors and transformers WERE linear devices. Have I been misinformed??

4. ### Energetic Thread Starter Member

Jan 3, 2011
33
0
Perhaps that is one reason i've been having so much trouble with this!! My textbook states:

Circuit elements in which the current flow is disproportionate to the applied voltage are said to have a non linear response to their inputs. These include rectifiers, diodes, transistors, valves and iron cored inductors/transformers.

I have shown it using a transistor in the end.

Apr 5, 2008
15,645
2,344
Hello,

When a transformer is driven into saturation, it will produce harmonics.

Bertus

6. ### Papabravo Expert

Feb 24, 2006
10,136
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Yes it will, because it is a "real" component. Many simulations are done with ideal components and many "real" components are linear over some operational range.

The definition given by the "textbook" is problematical because it defines linear in terms of a relationship between voltage and current. A reactive component can be linear in the "differential equation" sense while not having a linear relationship between voltage and current.

Integration and differentiation are in fact linear operations. Multiplication, absolute value, dead band, and limiting are quite clearly not linear operations.

7. ### Energetic Thread Starter Member

Jan 3, 2011
33
0
The first two sentences are helpful, thanks, the rest is gobbledigook to me sadly. I am not yet strong enough in the ways of the force.

I have seen a similar definition to that in several places. Why is there never just one straightforward answer in this business?

8. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
The key word in your textbook statement is "disproportionate". If the relationship between the applied voltage and current over the entire range of values is a constant factor then the device is linear. If not, then there is a non-linear condition.

A voltage amplifier is linear if the output voltage waveform is a faithful reproduction of the input waveform but with a greater magnitude which is in constant proportion (related by the voltage gain) to the input magnitude.

9. ### Georacer Moderator

Nov 25, 2009
5,142
1,266
A clipping amplifier is a good choice for your exercise, but you could still use the transformer is you can specify a saturation current in its options and turn it into a "more realistic" device.

10. ### Papabravo Expert

Feb 24, 2006
10,136
1,786
It is true that if you don't know what integration and differentiation are then understanding how a capacitor or an inductor behaves will be more difficult. You should understand multiplication. Absolute value, dead band, and limiting are things you can to to a signal that produce non-linear behavior. Read up and learn.

The answer to the last question is straightforward. Nature does not work that way.

11. ### Energetic Thread Starter Member

Jan 3, 2011
33
0
Just started differentiation today, brilliant fun! I will, as you say, read up and learn, but first i will go to the pub and have an ale or 3...

Cheers!

12. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
782
You might find that the consumption of alcohol impairs your ability to differentiate ....

13. ### Papabravo Expert

Feb 24, 2006
10,136
1,786
Go to bed early.
Get up late.
Work like hell,
And integrate!

14. ### Georacer Moderator

Nov 25, 2009
5,142
1,266
Oh, no! Loosewire's gone viral! Oh, the humanity...