Lecture - 19: Analysis of CE amplifier

AC Load line:

Consider the dc equivalent circuit fig. 1.

Fig. 1

Assuming IC = IC(approx), the output circuit voltage equation can be written as

The slop of the d.c load line is .

When considering the ac equivalent circuit, the output impedance becomes RC || RL which is less than (RC +RE).

In the absence of ac signal, this load line passes through Q point. Therefore ac load line is a line of slope (-1 / ( RC || RL) ) passing through Q point. Therefore, the output voltage fluctuations will now be corresponding to ac load line as shown in fig. 2. Under this condition, Q-point is not in the middle of load line, therefore Q-point is selected slightly upward, means slightly shifted to saturation side.

Fig. 2

GOTO >> 1 || 2 || 3 || Home