Chapter 4 problems

4.20

• We want to establish a DC operating point for the BJT. Writing a loop equation gives us -V_BB-V_in(t)+i_BR_B+v_BE=0. To form a load line, we will let v_in(t)=0 & i_B=0. Thus v_BE=V_BB+v_in(t) and i_B(t)=(V_BB+v_in(t))/R_B

• $V_{in}=-0.2,0,0.2$ for the minimum, Q-point and maximum values.

$v_{in}$ V	$V_{BE}$ V	$i_B$ uA
-.2	.45	2
0	.58	5
.2	.62	10

• Writing a loop equation for the output: $-V_{CC}+R_C{I}_C+V_{CE}=0$.

$v_{in}$ V	$V_{CE}$ V	$i_C$ mA
-.2	19	.8
0	16	2
.2	12	4

• $A_v\cong (19-12)/.4=12.5$