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close this bookAmplifier Teaching Aid (DED Philippinen, 86 p.)
close this folderLesson 9 - Small Signal Amplifier III
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View the documentThe AC load line

The AC load line

In previous lessons we used the dc load line to analyze biasing circuits. But an amplifier sees two loads, a dc load and a ac load. Now we will use the ac load line to understand the large signal operations.


Fig. 9-2: CE amplifier

DC values: VB = 1.8V, VE = 1.1V, IE = 1.1 mA, VC = 6.04V VCC = 10V, VCE = 4.94V

Without load: DC an ac load line are the same.

With load: rc = RC//RL

AC Load Line Construction

The following process shows you an easy method to get the ac load line:

1. Draw the dc load line

VCE (cut) = VCC - VE = 8.9V

2. Calculate and draw the Q point

IC = 1.1 mA

VCE = 6.04V

3. Draw a -temporary ac load line

VCE (cut) = VCC

4. Construct the ac load line

- parallel to the temporary ac load line
- passing the Q point


Fig. 9-3: Construction of an ac load line