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Design >> RF Design >> Designing class A RF power amplifier: load pull test
https://designers-guide.org/forum/YaBB.pl?num=1263798265

Message started by DoYouLinux on Jan 17^th, 2010, 11:04pm

Title: Designing class A RF power amplifier: load pull test
Post by DoYouLinux on Jan 17^th, 2010, 11:04pm

Hi all,

I am trying to design a class A PA in SpectreRF. I just would like to know that, in order to do a load-pull simulation, do you need to match the input of the transistor for a driving 50-ohm source before doing the load pull ?

For me, I think this is nonsense because we do not know the width and the bias of the transistor in advance. So I just bias the gate and the drain using ideal bias tee (big L and big C) and doing the load pull.

Do you think this is OK ?

Thank you very much,

DYL

Title: Re: Designing class A RF power amplifier: load pull test
Post by pancho_hideboo on Jan 18^th, 2010, 2:36am

DoYouLinux wrote on Jan 17^th, 2010, 11:04pm:

I just would like to know that, in order to do a load-pull simulation,
do you need to match the input of the transistor for a driving 50-ohm source before doing the load pull ?
For me, I think this is nonsense because we do not know the width and the bias of the transistor in advance.
So I just bias the gate and the drain using ideal bias tee (big L and big C) and doing the load pull.
Do you think this is OK ?

As far as S₁₂ is relatively small, it is OK.
See the followings. In this example, Load-Pull simulation is executed without input matching.
http://edocs.soco.agilent.com/display/ads2009/Load-Pull+Simulations

In Load-Pull Simulation, you have to control different impedance value as load impedance for each harmonics including fundamental.
Assume Z_load(n*f_in),n=1,2,3,4,5,....., generally you have to set these as different values each other.

However it is not so critical for your case, because your PA is class-A operation.

Also see the followings.
http://www.designers-guide.org/Forum/YaBB.pl?num=1242184095
http://www.designers-guide.org/Forum/YaBB.pl?num=1239997125

Title: Re: Designing class A RF power amplifier: load pull test
Post by DoYouLinux on Jan 19^th, 2010, 12:54am

Hi Pancho_hidebo,

Thank you very much for your reply and explanation. The information is also very useful to me :)

DYL