Hi guys I need some help with starting this problem. For question (a) don't I need to draw the mid-band small signal amplifier equivalent circuit given below to calculate the base current, emitter current and rPI?
I have solved this taking some approximations.
I calculated Ib using KVL in the base emitter loop. I found it to be 18.87 micro amps.
Then to find Ic I used Ic=ßIb. It turns out to be 1.887 mili amps.
And Ie = (ß+1)Ib=1.9mili amps.
To find Rpi =ß/gm(trans conductance)= ß/(Ic/Vt)=1.377Kohms.
But my Ic does not matches with the one given in the question. Will you please tell me what am I missing here?
You have not missed anything, Ie is 1.9mA. But is doesn't matter, for small-signal analysis we assume Ic =2mA.
And re = 26mV/2mA = 13 ohm so Rpi = 101 * 13 = 1.313k ohm. As you can see not much different from yours Rpi.
How are you calculating Ie is beyond my understanding. Check your Vbb and the equivalent resistance at base. You need to look at the pdf once again and understand what does this mean. Merely using formulas are not going to help. Clear your circuit theory concepts as well. You can use https://www.scribd.com/doc/37003448/Microelectronic-Circuits-6th-Edition .