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Electrical Engineering QUESTION #2164
Question 1
A BJT common-emitter amplifier has $\beta = 100$, $R_C = 4\,\text{k}\Omega$, and $I_{C,Q} = 1\,\text{mA}$. The small-signal voltage gain $A_v$ (neglecting $r_o$) is:
  • $-154$✔️
  • $+154$
  • $-400$
  • $-100$
Correct Answer Explanation
$g_m = I_C/V_T = 1\,\text{mA}/26\,\text{mV} \approx 38.5\,\text{mS}$. $A_v = -g_m R_C = -38.5\,\text{mS} \times 4\,\text{k}\Omega \approx -154$.