# Efficiency of a Class AB Amplifier

Discussion in 'General Electronics Chat' started by nathalie, May 9, 2011.

1. ### nathalie Thread Starter New Member

Jan 9, 2011
14
1
Efficiency of a Class AB Amplifier
How can i calculate the efficiency of a class AB amplifier circuit?

How can I determince Ps in the equation

efficiency = P(load) / Ps(supply) *100%

Thansk

2. ### Jony130 AAC Fanatic!

Feb 17, 2009
3,962
1,097
If the input signal is Vin = Vp*sin(ωt)
Then

$Ie=\frac{Vp}{R_L}*sin(\omega t)$

So the the instantaneous electric power form power supply is equal

$p_z=Vcc*i_e = \frac{Vcc*Vp}{R_L}*sin(\omega t)$

So to find average supply power you need to solve this

$Ps = \frac{1}{\pi} \int\limits_{0}^{\pi} Vcc*i_e d(\omega t)= \frac{1}{\pi} \int\limits_{0}^{\pi}\frac{Vcc*Vp}{R_L}sin(\omega t) d(\omega t)$

Last edited: May 9, 2011
3. ### nigelwright7557 Senior Member

May 10, 2008
487
71
It depends on the voltage out as to how much is power to the speaker and how much to the heatsink. Class AB is typically 60% efficient with 40% of power dumped into the heatsink.