# Transistor Analysis of a Common Base(?) BJT

Hey. I am a biomedical engineering student focusing on the biomaterials side. However, my university makes me take a few electrical engineering classes as well. So I am not very good at this. I was hoping if anyone could help me out.

As of rn, I have tried to use DC bias to find Ie. But I feel that Ie should be just 1mA due to the current source and Ic should be 0.5mA. But if I use Ic/alpha I get 505 microAmps. Could anyone point me in the right direction please?

• How do you calculate $I_C$ to be 0.5 mA if $\beta=100$? Apr 8, 2020 at 0:06
• The collector cannot go below the emitter voltage. The problem specifies that voltage. At most the collector current is $\frac{5\:\text{V}-\left(-700\:\text{mV}\right)}{10\:\text{k}\Omega}=570\:\mu\text{A}$. Given the emitter is having $1\:\text{mA}$ pulled out of it by force, this means the base current is at least $430\:\mu\text{A}$. So I don't know what the $\beta=100$ means in this case. The $-5\:\text{V}$ voltage reference is irrelevant, too. As the BJT is heavily saturated, so collector looks like a voltage source, the voltage gain is very close to 1 (slightly more, perhaps.)
– jonk
Apr 8, 2020 at 6:23
• It's a trick question : as an amplifier, it is broken.
– user16324
Apr 8, 2020 at 14:24
• @ThePhoton 5V/10K should get me Ic right? Apr 8, 2020 at 18:28
• Not if the BJT is biased into forward active mode. You can't assume the collector is at 0 V. Apr 8, 2020 at 19:50