# BJT analysis

1. Oct 31, 2016

### eehelp150

1. The problem statement, all variables and given/known data
Find Vc, Vb, Ve, Ib, Ic, and Ie
Vbe is 0.7V

2. Relevant equations
KVL

3. The attempt at a solution
Vb = (10*30k)/(80k) = 3.75V
Ve = Vb-Vbe = 3.05V
Ie = Ve/Re = 0.305A
Icmax = 10/(1010) = 9.9mA
Ie is much greater than 9.9mA, so this circuit is saturated. Is this correct?

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2. Oct 31, 2016

### Staff: Mentor

This is true iff the base current is zero or negligible.

It is better to apply Thévenin and say VB = 3.75 – IB×30k||50k

Q still turns out to be saturated, yes.

3. Nov 3, 2016

### rude man

1. Substitute labels for the resistors, like R1, R2 etc. Substitute actual values only at the end.
2. Write Σi = 0 at the base and emitter junctions. Let Ve = Vb - 0.75V. Gives you 4 independent equations in 4 unknowns.
3. Assume no saturation and solve for ib, Vb, Ve and Vc. If Vc turns out to be < Ve your equations were invalid and you have saturation.