Question 12.9: Calculate the efficiency of a class B amplifier for a supply...

Electronic Devices and Circuit Theory

Calculate the efficiency of a class B amplifier for a supply voltage of
$V_{C C}=24 V$ with peak output voltages of:

a. $V_{L}( p )=22 V$ .

b. $V_{L}( p )=6 V$ .

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Using Eq. (12.29) gives

a. $\% \eta=78.54 \frac{V_{L}( p )}{V_{C C}} \%=78.54\left(\frac{22 V }{24 V }\right)= 7 2 \%$

b. $\% \eta=78.54\left(\frac{6 V }{24 V }\right) \%= 1 9 . 6 \%$

Notice that a voltage near the maximum [22 V in part (a)] results in an efficiency near the maximum, whereas a small voltage swing [6 V in part (b)] still provides an efficiency near 20%. Similar power supply and signal swings would have resulted in much poorer efficiency in a class A amplifier.

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