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ADS Cascode Power Amplifier Loadpull Problem

simon880106

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Hi,

I try to Loadpull a cascode amplifier using (tsmc90)
1656143404657.png

with Frequency=28GHz, Pavs=16dBm, VDS=3.3V for each transistor, VGS=0.8V
but after Loadpull Simulation, I got negative PAE and the maximum output power is lower than Pavs_dBm
1656143438968.png

Can someone help me if there is problem with my setting. Thanks!
 

BigBoss

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How do I know the transistor can't work at such a high frequency?
You have to check fT value. If your operating frequency is 28 GHz, the transistor must have at least 50-60 GHz fT.
I believe you know what fT means. I don't know TMSC's 90nm CMOS Process but it seems hard to work @ 28GHz.
Only GaAs or InAlP or equivalent processes can work at that level. Some SiGe and GaN processes have been reported.
 

simon880106

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You have to check fT value. If your operating frequency is 28 GHz, the transistor must have at least 50-60 GHz fT.
I believe you know what fT means. I don't know TMSC's 90nm CMOS Process but it seems hard to work @ 28GHz.
Only GaAs or InAlP or equivalent processes can work at that level. Some SiGe and GaN processes have been reported.
Thanks for the help!
I check the fT with a single transistor, and the value of fT is around 50-80 GHz.
(VGS=3.3V)
Is it possible for the transistor to work at 28 GHz?
1656319892742.png

1656319937848.png
 

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