BJT and finding Resistance

Thread Starter


Joined Mar 8, 2011
If I had this circuit:

If Rb had zero current flowing through it. I need to calculate the input resistance looking into the BJT. Rin=Vin/Iin, Vin is input voltage to BJT.

The bottom is voltage divider. I know the 10k resistor before the BJT will be va and vb on each side with Iin going through. So if Rin=Vin/Iin = vb/Iin.
Would Iin=voltage through divider - vb / 10k?