BJT problem

Discussion in 'Homework Help' started by sportguy98, Nov 10, 2013.

1. sportguy98 Thread Starter New Member

Sep 10, 2013
5
0
Hello,

I am having difficulty with this particular problem involving a BJT circuit. I was able to solve all other BJT problems except for this one.

The teacher does give the solutions in hints, but I would like to understand why it is solved this way.

Here is the problem:

I wrote all the KVL equations... so KVL for base-emitter, KVL for base-collector and KVL for emitter-collector.

I also know all the formulas like IE = IB + IC, IC = B*IB, IC = A * IE, etc.

My problem is with the R1 and R2 resistances. If one them was grounded I would not have any trouble, but since they are, I do not know how to proceed or what simplifications to be made.

Thanks again !

2. LvW Active Member

Jun 13, 2013
674
100
My problem is with the R1 and R2 resistances. If one them was grounded I would not have any trouble, but since they are, I do not know how to proceed or what simplifications to be made.

The two resistors form a voltage divider - if one of them is grounded or not.
There is - in principle - no difference in the calculation method.
However, you should be aware that you are free to choose a suitable impedance niveau for both resistors. A common rule of thumb is that the current through R1 is selcted to be approximately 10*Ib=10*Ic/80.