Class A PA PAE with resistive load & inductor load

[MI3talk]

Class A PA PAE with resistive load & inductor load quest


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Hi all,

I think I have a dumb question to ask.

over couple of days, I was trying to understand why Resistive load Class A PAE is 25% and Class A with Inductive load is 50%.

It was told that inductor can swing rail to rail, but why? It that because the current direction could go from 0 to positive rail and back down to 0 and swing to negative rail again?

Can someone please explain in details with load line analysis?

 

[vfone]

The efficiency of Class-A Power Amplifier is degraded by the on-state resistance or saturation voltage of the transistor. It is also degraded by the presence of load reactance, which actually requires the PA to generate more output voltage or current to deliver the same power to the load.

 

[BigBoss]

Load line with inductive (or capacitivie) is not a straight line but ellipse..( depending on reactance value)
Therefore current that flows thru load is not purely real instead reactive so some power returns back to the amplifier even tough the amplifier is well matched.
In addition to, there will be some additional mismatch (in terms of power ) and that's why load is not fully delivered to the load..

It should be prevent to use reactive loads..