BJT Biasing

The voltage-divider bias with an emitter resistor is the standard approach:

$V_B = V_{CC}\frac{R_2}{R_1 + R_2} \qquad I_E \approx \frac{V_B - 0.7}{R_E}$

Because $I_E$ is set by $V_B$ and $R_E$ — not by β — the operating point stays put when β varies or the transistor heats up. Make the divider current at least about 10× the base current.

Aim the quiescent collector voltage near the middle of the available swing for maximum undistorted output. Bypassing $R_E$ with a capacitor restores AC gain while keeping DC stability.