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extracting RF power transistor in/out impedance with Spice

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maniana

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rf power transistor

Hi,
Can someone help on how to extract LARGE Signal input and output impedance of
an RF transistor with PSpice?
I have a spice model of a transistor and I want to know its impedance at certain frequency and bias points ?
What should my schematic look like, what simulation to use?
Are there any application notes on this matter?
 

rf transistor spice model

As I know so far, there is no such way to predict accurate large signal impedance.
 

pspice output impedance

If it is not possible, as you say, then how is possible harmonic balance simulation or "load-pull" with microwave simulators such as AWR?
I have a PSPice model of a transistor (eg. BFG591, BFG540W), how do I get to know the optimum input impedance or the output impedance? in particular the reactance component of it.
 

output impedance pspice

Yes, there are many large signal models for nolinear simulation. For the transistors you mentioned, you can go ahead with your model.
 

input impedance measurement spice

Yes , I have the spice models for these transistors, but my point is that I still don't know the input and output impedance of those transistors. AWR will simulate the circuit but then if I put the component values to pspice I get completely different results. I made the circuit PCB and I got another result that is completely different from simulations. Real world pcb has completely different frequency characteristic.
From simulation my amplifier should work 300MHz-350MHz with a flat gain characteristic and the real circuit works from 290MHz to 500MHz with five peaks, plenty of resonances etc... and a gain thats nowhere near the simulation.
 

ads spice rf hb different

Hello maniana,


Yes, you can do Large Signal impedance measurements in AWR Microwave Office & its simple...

First import the spice model then create new schematic & add the
Ideal Bias Tee's at input & output & bias using the source blocks...
Finally add HB port at input & set the power in in dBm then add measurement
such as Lssnm for input & output on smith chart or rectangular plot...

Thats it done....

If not send me MWO project file (*.emp) & spice model (*.cir), I will construct the same & send it to you....


Note: Large Signal S-Parameter at Harmonic: LSSnm is a Nonlinear measurement available in power section...

---manju---
 

inout impedance

maniana,
Polyfet shares ADS and AWR designs to extract Zin and Zout impedance of a transistor from Spice Model. The design contains optimization and goal parameters set up to tune input and output circuit for maximum power and gain. Both ADS and AWR versions are allowed for dwonload at their site.
Take a look; http://www.polyfet.com.

With Regards,
WM3
 

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