How to simulate ft/fmax in AWR(microwave office)?

[selwyn008]

how to simulate fmax

Hello, guys
I wanna see how ft/fmax changes with different Ic to choose best bias for device.
How can I plot this curve in Microwavr Office?

I used the transit time（TFF) to simulate ft：
TFF=TF*{1+XTF*(if/(if+ITF))^2*exp(Vbc/(1.44*VTF))}
and if is the ideal forward diffusion current，if=IS*(exp(Vbe/(NF*Vt))-1)
Then， ft=1/(2PI*TFF)。
However，the simulated ft_VS_Ibias is not a 2nd order curve with a peak，but a monotone decreasing equation。
I don't know why， any help for me?thanks very much

selwyn

 

[Manjunatha_hv]

how to simulate peak ft

Hello,

Follow below steps...
set tau, or Gm as sweep variable in schematic add output equation for ft & then add the IDC measurement to Ic then plot on a graph..

OR

take separate ft/fmax measurement with the equation and a separate measurement for Ic...
Then plot both measurements using Data -> Plot Measurement 1 vs Measurement 2: PlotVs

---manju---

 

[selwyn008]

awr microwave equation if

Hi，Manju
thank you very much, but what I really want to know is the exactly ft/fmax equation for simulation. Can you give me some instruction?
Thanks for help.

selwyn

Hello,

Follow below steps...
set tau, or Gm as sweep variable in schematic add output equation for ft & then add the IDC measurement to Ic then plot on a graph..

OR

take separate ft/fmax measurement with the equation and a separate measurement for Ic...
Then plot both measurements using Data -> Plot Measurement 1 vs Measurement 2: PlotVs

---manju---