#### efevi

##### Newbie level 5

In the analog electronics project, we are required to build an audio amplifier. The restrictions are:

- IC's will not be used.

- At least 6 watts will be delivered to 8 ohms speaker.

I have made 2 designs, one class ab and one class d amplifiers, in simulation everything works fine, i can get pure sinusoids and upto 100 watts on speaker, with +-25 double supply rail and, bridge configuration to double the speaker voltage if necessary.

However there is one little problem: The power supply that i use is Agilent E3631A, which gives max + - 25 volt limited by 1 A current for each of supplies. This limited current here means that (i suppose): The power cannot give more than 1 Amps in any instant of time, which will clip the current seen on power supply, and on the rest of the circuit at 1 Amps, if the project is not designed considering this fact.

Therefore, in order not to clip the audio signal, I need to pass at most 1 amps sinusoid across speaker, which will give (1/sqrt(2))^2*8=4 watts.

Now since i use +-25 supplies the 1 amp dc means 50 watt is driven from the supply. Where the rest of power goes is : 1. the driven current is not dc but ac with lower effective value, which means the driven power is much less. 2. in class ab the practical efficiencies are around 60-70% if and the rest is dissipated on the rest of circuit.

I think class ab cannot do much about this current limiting. I am not sure about class d.

I would be very thankful if you could have some comments. Am i correct on these, and may there be anyway to get through these? In addition, i cannot model the power supply such that it limits currents over 1A, in spice. How can i do that?

Thank you for reading