harmonic distorsion causes

[p11]

can anyone help me by answering what is harmonic distorsion???:-|?when does it occur and why?and how to eliminate it?please try to explain in easy words.....=)

 

[dick_freebird]

Every nonlinear element (esp. diode junctions) does a
frequency generation by mixing / multiplication, if you let
it. For true linearity you can only have straight addition
or subtraction. Things like clipping make an addition, no
longer straight. Often the core circuit is not all that linear
and feedback (using very linear elements) is used to get
the outcome linear; this is subject to other issues itself
because gain is always finite, even socket contacts can
be low level rectifying and corrupt all the perfect (as if)
piece-parts.

 

[LvW]

how to eliminate it?please try to explain in easy words.....=)

In addition to dick´s explanation: It can be "eliminated" (in the frequency domain that means: suppression of unwanted harmonics) using lowpass or bandpas filtering.
However, in reality "eliminated" means to reduce THD to a level which fulfiils the particular requirements.
No ideal filtering and no total elimination is possible.