# How to find the density of collector saturation current?

1. Feb 25, 2015

### CKaiL

1. The problem statement, all variables and given/known data
Given the following formula for saturation current

2. Relevant equations

3. The attempt at a solution
I am able to find the value for Dn , q , WB , ni and N AB except for the A(cross sectional area)

2. Feb 25, 2015

### phinds

3. Feb 25, 2015

### CKaiL

Find the collector saturation current density since I have the following
Doping in the emitter, NDE = 1018 cm-3,
Doping in the base, NAB = 2×1016 cm-3,
Diffusion coefficient of holes in the emitter, Dp = 1 cm2/s,
Diffusion coefficient of electrons in the base, Dn = 10 cm2/s,
Diffusion length of holes in the emitter, Lp = 0.300 μm,
Diffusion length of electrons in the base, Ln = 20 μm,
Width of the neutral region in the base, wB = 1 μm.

4. Feb 25, 2015

### phinds

You have simply restated exactly the same problem but with specific values. You don't know the area so you can't finish the computation, right? Would you like for us to make up a cross section for you? Ok, use 1 square meter.