So basically I was studying microelectronics written by Razavi and stucked with the part 5.2.2 (Resistive Divider Biasing)
The text shows 2 examples shown below.
It asked the value of Ic and the difference between Fig A and B is that it has a different value of R1 and R2, respectively, which is 17k / 8k and 170k / 80k.
I had no difficulty getting Ic in fig A, since I used a formula Ic = Is*exp(V_be/V_t)
but when it comes to Fig B I went wrong because I_b, the base current, was not negligible and I had to get a V_thev and R_thev.
So I was wondering when should I use the Thevenin equivalent circuit?
and what is the standard to use it, so to say what value of R1 and R2 makes I_b considerable?
The text shows 2 examples shown below.
It asked the value of Ic and the difference between Fig A and B is that it has a different value of R1 and R2, respectively, which is 17k / 8k and 170k / 80k.
I had no difficulty getting Ic in fig A, since I used a formula Ic = Is*exp(V_be/V_t)
but when it comes to Fig B I went wrong because I_b, the base current, was not negligible and I had to get a V_thev and R_thev.
So I was wondering when should I use the Thevenin equivalent circuit?
and what is the standard to use it, so to say what value of R1 and R2 makes I_b considerable?