# BJT Lab help(2)

1. Mar 5, 2014

### go2255

This is the result from a lab,but I am not sure the results are correct.

I guess the combination of R1=10k and R2=10k is under linear region,but how come the calculated Ib is zero.

For combination of R1=10k and R2=1k,Idon't know why the Ie is negative.Negative value means error?Is it the cut off mode?

And for combination of R1=1k and R2=10k,it should be in saturation?
I guess either the measured or calculated result is wrong.What is the problem?

Also,there are many differences(highlighted).Is my calculation wrong?

File size:
16.3 KB
Views:
91
2. Mar 5, 2014

### Staff: Mentor

How did you get the formulas for I_C and I_E? One of them is wrong, but as there is no explanation where they come from and what you did there it is hard to tell which one.

3. Mar 7, 2014

### rude man

Just to give you general guidance, your results should be
Vb = R1/(R1+R2)10V
Ve = Vb - 0.7V
Ie = Ve/Re
Ib ~ 0
Ic ~ Ie
Vc = 10V - Ic*Rc
Vrc = 10V - Vc

EXCEPT for R1 = 1K, R2 = 10K. For this configuration the transistor is saturated and the computation is more laborious. If you want to attempt it, assume Vc = Ve, write 2 equations in unknowns Ib and Ve. Vb is still Ve + 0.7V.