# BJT analysis question

1. Oct 31, 2016

### eehelp150

1. The problem statement, all variables and given/known data

2. Relevant equations
KVL

3. The attempt at a solution
This is the solution given:
VB = (VCC*30k)/(70k+30k) = 3V
Why is a voltage divider being used to find Vb?

2. Oct 31, 2016

### Staff: Mentor

Your question should be in the problem statement, not the attempt.

Are you sure that VB is the same as Vb? Looks to me like a determination of a Thevenin equivalent for the base voltage supply. Was there also a Thevenin resistance calculated (paralleling the 30 k and 70 k resistors)?

3. Oct 31, 2016

### eehelp150

VB is Vb.
Thevenin resistance was calculated for 30k and 70k.

4. Nov 1, 2016

### LvW

What is your task? To find the DC voltage VB at the base?
Don`t forget that you have a loaded resistive voltage divider - loaded with the transistor base current.

5. Nov 1, 2016

### Staff: Mentor

This is what I imagine the author of the solution was going for:

With $V_B$ and $R_B$ being determined as the Thevenin equivalent of the base voltage divider.