What is the OIP3 of LDMOS?

[tony_lth]

Hi, ALL,
Normally there is no spec on OIP3 of LDMOS.
But I need to guess one so that I can replace some current PA.
Say, attachment is one PA, LDMOS of Mitsubishi, how to guess its OIP3?
It is used in some GSM basestation.
Best,
Tony Liu

 

[vfone]

From the plots in the datasheet we see the P1dB, which is about +42dBm.
So, you can assume that the OIP3 is equal or greater than +52dBm.
2nd and 3rd harmonic plots cannot give much information about OIP3. I've seen PAs with low 2nd and 3rd harmonics but with poor IP3.
IP3 depends very much by the impedance termination of the bypassing circuit (filtering) of the PA bias. This impedance should be very low at the frequency equal to the spacing frequency of the two tones used for measuring IP3.

 

[tony_lth]

Thanks, Vfone.