I am having trouble calculating values for this audio amplifier. Input comes from AVR PWM operating at 44.1 kHz with high being at 3.3V. The speaker is 8 Ohm and speced for 1 Watt.
First two transistors, Q1 and Q2 provide high input impedance for PWM signal, while Q3 and Q4 form push-pull amplifier for the speaker. L1 and C1 form low pass filter, to convert PWM into analog signal.
First off, I am not enterely sure this is the best/correct approach, so if anyone has any better ideas let me know. The second thing is, I am not sure if I correctly calculated values for these resistors. These are the values I calculated earlier (R2, R3 = 47 Ohm, R1 = 330 Ohm, R6 = 470 Ohm, R5 = 1 kOhm, R4 = 470 Ohm).
I would really appreciate if with your anwser you could provide details and explanation of the calculations.
Also note, that AVR pin can source/sink maximum 20mA of current.
Any help is greately appreciated!