I'm trying to understand and learn the basics of audio "tech". For a simple test project, I wanted to connect an electret mic to an amp to a speaker to see if I can get any output.
For the electret mic preamp circuit, I used this document as the basics: https://www.ti.com/lit/pdf/tidu765
For you conveninece, I pasted the schematics here too.
I have a 0.5W, 8ohm tiny speaker.
- when they say it's a 8Ohm speaker, is that 8Ohm DC or at some kind of standard frequency in an AC circuit? (multimeter did show 8 Ohm) So I guess I'm asking if it is an impedance value or not?
- same question for the watts. If my circuit is a 5V circuit (op amp out will be oscillating around 2.5V), what kind of resistor value do I need on the output to drive this speaker?
- when calculating this resistor value, should I consider the peak-to-peak voltage change of the output signal or should I just go with theoretical maximum of 2.5V?
- I'm using an LM358 which seem to have a max output current of 20mA, am I reading the datasheet correctly?
- If 20mA value is correct, what is the P of the output (I don't know what V value to consider, peak-to-peak or Vcc)
- In any case, it seems that this opAmp cannot drive 0.5W. The speaker doesn't even quack Am I correct assuming that the cause of that is the insufficient power to it?
- If I used to BJT on the output to buffer some extra juice, could that be a solution?
Thanks a lot for your answers and the time you put into them.