Question

QUESTION 2 Determine whether the transistor n figure 2 is saturated RC 1 5kn RB BDC 120 VCC 12kΩ 9V VBB 85 V Figure 2 [9]

Answer 1

Let assume BJT in active region. i.e, V_BER = 0.7V, V_c > V_B > V_E and V_CE > 0.2 V. rightarrow V_BB + I_B R_B + B_BE = 0 [because Mesh eq in Bale - Emitter loop] -8.5 + 1_B (12 times 10^3) + 0.7 = 0 I_B = 8.5 - 0.7/12 times 10^3 I_B = 0.65 mA rightarrow I_C = beta I_B I_C = 0.078 A rightarrow I_E = (1 + beta) I_B I_E = 0.07865 A rightarrow V_CC + I_C R_C + V_CE = 0 [because Mesh eq in collector - Emitter loop] -9 + (0.07865) (1.5 times 10^3) + V_CE = 0 V_CE = 9 - 117.975 V_CE = -108.975 V \r\n rightarrow V_CE < 0.2V, so BJT operator in saturation region i.e., V_CE = 0.2 V and V_BE = 0.8 V -V_CC + I_C R_C + V_CE = 0 [because mesh eq in collector - Emitter loop in saturation] I_C = V_CC - V_CE/R_C I_C = 9 - 0.2/1.5 times 10^3 I_C = 5.86 mA