- Joined Jan 1, 2016
This is the information provided on top of the page: A sine shaped signal with a frequency of 100 Hz and an amplitude of 1.5V is put in the circuit. The current amplification of the transistor is B = 200. A SPICE simulation proivdes for Ic(Q1) a current of 18 mA. Provide your calculations down to four significant figures.
a) Calculate the cutoff frequency (fc).
This is my question. Where does the 20.1 kOhm coming from? He calculate "little re" as 25.8 mV / 18 mA = 1.433 Ohm. Now, this is what I did next, I added "little re" to R4 and multiplied it by 200 ( (1.433 Ohm + 100 Ohm) * 200) and got as a result 20286.6 Ohm, rounded this is 20.3 kOhm.
So, what is wrong with my approach?