Saturday 11 May 2019

Class AB power amplifier


I have implemented a class AB amplifier. The schematics are below.


My class AB amplifier schematics



As you can see, my \$V_{cc}\$ is only 1V. How come I can still suppy 2.8 amp to the 4 ohm speaker/load? Is it a bug in MultiSim, or did the input signal (16V pk AC) made its way to the speaker? As far as I know, the voltage output in the load cannot exceed \$V_{cc}\$.


Both transistor appear to be in good placement/direction, but I've seen other configurations in which the transistors are reverted.


Here is a link to my schematic.


Safety question: Is it ok for my 4 ohm speaker pass the whopping 2.8 amps? Is it common for power amplifiers to do that?



Answer



That will not work. You cannot drive the the transistors above the collector voltage otherwise the Vbc becomes forward biased.


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