Determine RC and RB for a fixed-bias configuration if VCC = 12 V, β = 80, and with . Use s...

Calculate base resistor \(\left(R_{B}\right)\).

$$ \begin{aligned} R_{B} &=\frac{V_{R_{B}}}{I_{B}} \\ &=\frac{V_{C C}-V_{B E}}{I_{B}} \end{aligned} $$

Here,

Supply voltage \(\left(V_{C C}\right)\) is \(12 \mathrm{~V}\).

Base-emitter voltage \(\left(V_{B E}\right)\) is \(0.7 \mathrm{~V}\).

Substitute \(12 \mathrm{~V}\) for \(V_{C C}, 0.7 \mathrm{~V}\) for \(V_{B E}\) and \(31.25 \mu \mathrm{A}\) for \(I_{B}\) in the expression of base

$$ \begin{array}{l} \text { resistor }\left(R_{B}\right) . \\ \qquad \begin{aligned} R_{B} &=\frac{12 \mathrm{~V}-0.7 \mathrm{~V}}{31.25 \times 10^{3} \mathrm{~A}} \\ &=\frac{11.3 \mathrm{~V}}{31.25 \times 10^{3} \mathrm{~A}} \\ &=361.6 \times 10^{3} \Omega \\ &=361.6 \mathrm{k} \Omega \end{aligned} \end{array} $$

Therefore, base resistor \(\left(R_{B}\right)\) is \(361.6 \mathrm{k} \Omega\), hence the nearest standard value of resistor is \(360 \mathrm{k} \Omega\).

Calculate collector resistor \(\left(R_{C}\right)\).

$$ \begin{aligned} R_{C} &=\frac{V_{C C}-V_{C}}{I_{C}} \\ &=\frac{V_{C C}-V_{C E_{0}}}{I_{C_{Q}}} \end{aligned} $$

Here,

Source voltage \(\left(V_{C C}\right)\) is \(12 \mathrm{~V}\).

Collector current \(\left(I_{C_{Q}}\right)\) is \(2.5 \mathrm{~mA}\).

Collector-emitter voltage \(\left(V_{C E_{Q}}\right)\) is \(6 \mathrm{~V}\).

Substitute \(8 \mathrm{~V}\) for \(V_{C}, 18 \mathrm{~V}\) for \(V_{C C}\) and \(3.9 \mathrm{k} \Omega\) for \(R_{C}\) in the expression of collector

$$ \begin{array}{l} \text { resistor }\left(R_{C}\right) . \\ \qquad \begin{aligned} R_{C} &=\frac{12 \mathrm{~V}-6 \mathrm{~V}}{2.5 \mathrm{~mA}} \\ &=\frac{4 \mathrm{~V}}{2.5 \times 10^{-3} \mathrm{~A}} \\ &=2.4 \times 10^{3} \Omega \\ &=2.4 \mathrm{k} \Omega \end{aligned} \end{array} $$

Hence, the of collector resistor \(\left(R_{c}\right)\) is \(2.4 \mathrm{k} \Omega\).