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ADS Cascode Power Amplifier Loadpull Problem

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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!
 

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.
 

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
 

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?
View attachment 177121
View attachment 177122
hello,i am using ADS the design guide -amplifier -DC and bias point simulation -BJT-ft-fmax-vs Bias cell, when I change the BJT from ideal one to the pdk npn,I can’t get the full result (only get two) ,

I check the error from the plot:Maximum frequency of oscillation (fmax) and other plot(shown in the above figure)
, all the reported error are the same as below:
While evaluating "LcsGetNewExpName1":
Operation "[ ] sweep access", index out of range in dimension 1, independent "freq" must use an index in the range 0 <= index < 0

Could you tell me how to solve it?

Thanks in advance!
 

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