I am new to AAC. Our instructor gave us a pwr amp circuit last Friday and asked us
to figure out what was wrong. I posted in the homework forum but maybe I should
have posted here.

I have uploaded the spice simulation schematic.

I expected the output power to be approx = (12V*.8*.5*0.707)^2 / 16Ω = 720 milliwatts
rms (someone in other form helped me with this piece)

spice result is 199 milliwatts avg
thd of 5.85%
peak o/p volt of 2.5 with 0.5 volts in

we have to build this amp this week but I wanted to clarify these points first

would anyone have time to help me?

thx

 

See: https://forum.allaboutcircuits.com/threads/problem-with-amplifier-assignment.158489/#post-1377835

 

See: https://forum.allaboutcircuits.com/threads/problem-with-amplifier-assignment.158489/#post-1377835

this is the forum for amplifiers that is why I am asking here

 

The question you ask is a homework question and there is a separate forum for those questions.
Further the same question has already been asked and answers discussed in the thread I linked.

 

Play around with the values and read the threat linked. The .step command can be useful. Good luck

 

Thread*

 

Play around with the values and read the threat linked. The .step command can be useful. Good luck

It is my thread that you sent a link for.

I played with the values and had new questions but no one replied.

 

The question you ask is a homework question and there is a separate forum for those questions.
Further the same question has already been asked and answers discussed in the thread I linked.

it was my thread and I had more questions but no one replied

 

It is my thread that you sent a link for.

I played with the values and had new questions but no one replied.

What did you try changing? Did it change the output power?

 

it was my thread and I had more questions but no one replied

I see no new questions in that thread.

 

What did you try changing? Did it change the output power?

I changed the Q3, bias resistors up and down in various combinations and the output voltage and power changed but the transient
curve for voltage is still skewed, that is, the + peak is 1.6 volts while the - peak is 2.0 volts.

I uploaded the simulation again.

 

One thread is enough.
https://forum.allaboutcircuits.com/threads/problem-with-amplifier-assignment.158489/#post-1377835