find transistor high frequency emelemts

[baby_1]

How can find
1-Cje
2-Cpi
3-Cm

 

[goldsmith]

Dear baby_1
Hi
Can you tell ,me more explanation about what you need , exactly , please ? i think you want to know that how to find the values of internally capacitors of a bjt . if yes , you can find them in datasheets , simply .
Best Wishes
Goldsmith

 

[baby_1]

Hello Dear Goldsmith
as matter of fact yes, because i read more reference about the internal capacitors but none of them don't tell more about how can we find them.according the datasheet we know the capacitance of input and output value.but as you know these value changed by base voltage. i want to know the exact value of them at a base voltage.
Thanks

 

[goldsmith]

exact value of them at a base voltage.

Is your mean that , you want find it's value instead of specific voltage ? if yes , with miller laws , you can do it .
C equal=C*A
Wish you the best
Goldsmith

 

[baby_1]

could you tell me more about it?
please give me an example with a real datasheet and transistor information such as 2n3904.
https://www.fairchildsemi.com/ds/2N/2N3904.pdf
Thanks

 

[goldsmith]

See below , please :
**broken link removed**
The red section . the designer , calculated it , instead of 5 volts and 0.5 volts at 1MHZ .
Good luck
Goldsmith

---------- Post added at 21:37 ---------- Previous post was at 21:36 ----------

By the way , these specifications are instead of small signal analysis .

 

[baby_1]

Thanks Goldsmith but its only for a same voltage test i want to find it for all base voltage condition

 

[goldsmith]

how much precision do you need ? ( my mean is for that capacitor ?) if the precision that you need isn't very particular , you can use a variable supply ( function generator ) and then , measure it ! ( alike with the action that manufacturer did ) .
Best Luck
Goldsmith

 

[baby_1]

Thanks Dear Iranian friend
i found the answer of my question with the curve in the datasheet.
could you help me on this?
https://www.edaboard.com/threads/250148/