What does clipping and knee mean in regards to diodes?

[gundam]

About diode

Hi,

I got this from another part of the forum, just like to post here for advice.

<The LO signal should have sufficient RF level to drive the diodes into clipping>
What is the word "clipping" means?

<This means conversion loss will be nearly independent of LO drive level. This happens above a certain level, a 'knee'. This means the RF output level of the mixer is more or less independant of the LO drive level and any AM modulation of the LO signal will be suppressed. >

What is the meaning of the 'knee'

Thanks

 

[sweet_nth]

Re: About diode

clipping means that u limit the voltage swing of a signal.. i.e. u "clip" the voltage signal to reduce the peak.. and u can do that using diodes, u can search online for "diode clipping circuit" to see a circuit that does that,,

i dont know what a knee is ??

 

[flatulent]

Re: About diode

knee is a vague term for where a curve changes shape. The LO drive should be high enough to drive the diode to full off (reverse bias) and full on (several mA of forward current flow.)

 

[tshankar501]

Re: About diode

Instead of explaining the place where the curve changes as the knee we could explain that knee voltage as the breakdown voltage where the voltage is constant and large current flows. this happens if we apply reverse voltage to the diode

 

[truebs]

Re: About diode

Some books and authors refer the voltage after which diode starts conducting (0.7 for Si and 0.3 for gi ) as Knee Voltage .