im stuck solving the RB1 RB2 values is a classic discrete BJT circuit bias arrangement. Im sure its a simple thing that im just not seeing.
Circuit values given are
V collector to emmiter =5v
Rc, RB1, RB2.
To start with to simplify things i have ignored VT and VA.
I can determine Rth=(R2.R1)/R1+R2=R1||R2
and Vth=(R2.Vcc)/(R1+R2) = R2.10/(R1+R2). i can determine Ic=(100/101)(Ie)=1.49mA and Ib=Ith=1.49mA/100=0.0149mA or 0.001mA depending if i use KCL or ib=Ic/beta.
simulate this circuit – Schematic created using CircuitLab
Now i apply KCL from ground through Vth, Rth,and out at base voltage = 2.2. and i end up with a ratios R1/R2=(7.8-IbR1)/2.2=(7.8-0.0149mAR1)/2.2.
From here i am stuck be cause i have 2 unknowns R1 and R2 and don't know any other equations i can apply to solve a value? I have also done a KCL at the RB1 RB2 BASE node and i end up with the same ratio. and i cannot substitute the KCL into the KVL because i end up with 0=0.
Also what i have learned from making the KVL KVL subsitution mistake is that you cannot substitute KVLs into other KVLs and KCLs because you end up with 0=0. is this always the case?