question about gain expansion of PA

[RF_PA]

gain expansion

hi everybody
I'm designing PA for 802.11b,but i find it has the problem of gain expansion, as a
result, the 1dB point is lager the normal value, in other words, the linearity is bad,
how can i solve it? thanks

 

[kspalla]

I guess the PA bias is not optimum.
Try to play with bias voltage and current to suppress the gain expansion.

 

[RF_PA]

Thanks

 

[ChaoFan]

Normally, gain expansion generated by Vgs modulation. Maybe you can increase the Idq to a real class A PA to see what will happen.

 

[ryanbowen]

shunt a cap in bias circuit will be better to gain expansion