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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?

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    \$\begingroup\$ Your text says the load is 8 ohms but your schematic says 4. Your supply rail is a fraction of the specified input swing. No negative feedback, but positive feedback. This monstrosity will both clip and oscillate. I suggest you go back to the books. Not a real question. \$\endgroup\$
    – user207421
    Nov 20, 2012 at 22:25
  • \$\begingroup\$ edited. 8 ohms was a typo. sorry \$\endgroup\$
    – vvavepacket
    Nov 21, 2012 at 10:45

2 Answers 2

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

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You appear to have connected the output directly to the input. Even if that is corrected, the input signal will go to the load through the base-emitter junctions of the transistors.

A class AB output stage will have a voltage gain of alpha, which is slightly less than 1.

I'm not sure what you're trying to accomplish by driving your circuit with 16V.

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