Hello, in the attached picture for the circuit,
I wanted to ask if V2/Vin is indeed 10/11 or would we need to include r as well
Thanks

 

No, for sure V2/Vin is not equal to 10/11 you have to include r_pi = rbe = β/gm

 

Alright so r_pi = 500 ohm
I know vo/v_pi is -100β/ rpi

so if v_pi/vin isnt 10/11, is it Vpi/Vin = (r_pi//10k) / [(r_pi//10k) + 1k]
so v_pi/Vin = 0.25 instead of 10/11 ?

Thanks

 

What is V2?

 

sorry v2 is v_pi on the diagram I wrote v2 earlier because I didnt have the symbol for pie

 

sorry v2 is v_pi on the diagram I wrote v2 earlier because I didnt have the symbol for pie

Okay. But you should define the terms you use, either in text (such as just saying, "V2 = v_pi on the diagram") or by annotating the diagram with V2. Don't make readers guess what you mean -- engineering isn't about guessing. Sure, much of the time we can guess correctly, but sometimes we won't and then people aren't on the same page and chaos ensues.

As for the symbols, you can use the big S icon on the reply toolbar to bring up a long list of symbols that you can insert into your post. The font leaves a lot to be desired, but π is one of the available symbols.

 

Will do next time,
just to elaborate, Im trying to get vo/vin by doing (vo/v_pi) (v_pi/vin)
I already have vo/v_pie
so previously had v_pi/vin = 10/11
another attempt is v_pi/vin = (r_pi//10k) / [(r_pi//10k) + 1k] // rd = 500 ohm which ends up v_pi/vin = 0.25
I wonder if either is correct or how I can correct this
thanks

 

If r_pi = 500Ω we have V_pi/Vin = (0.5kΩ||10kΩ)/(0.5kΩ||10kΩ + 1kΩ) = (1/(1/0.5+1/10))/(1/(1/0.5+1/10) +1) = 0.3225[V/V]

 

Thanks Jony much appreciated.

 

Notice that this is nothing more than the loaded voltage divider. Vo = Vin * R2/(R1+R2)
Where R2 = 10kΩ||0.5kΩ