Electronic – How to calculate the collector resistor of this emitter circuit


My supply voltage is +10 V, collector current at my bias point is 5 mA, base current is 28.8 uA, amplification is 173.3

enter image description here

I already calculated the base resistor to \$R_1=\frac{V_{CC}-V_{BE}}{I_b}\$ and it seems to be right.

These are the correct values according to the solution:

  • \$R_1=322\text{ kΩ}\$
  • \$R_2=2140\text{ Ω}\$

I cant seem to find out how to get R2.

Best Answer

Based on the numbers you have, and assuming you want the collector to rest at 50% of the supply voltage. then Ohm's Law:

E = I x R

R = E / I

R2 = (Supply/2) / 0.005 A

R2 = 5 / .005

R2 = 1 K

Note that the circuit will not actually work. Biasing the base with a single resistor is called dangle biasing, and is severely unstable. The gain of the transistor changes with temperature, with changes in collector current, and from part to part.