I have to design a circuit that amplifies a sine wave with either a AD8616 or a LTC6256 (currently using the AD8616) to a 50 ohm loudspeaker and a rated power of 0.5 W. I'm a novice when it comes to analog electronics and I'm getting very confused trying to design a circuit for my needs. I'm not a native English speaker too, so please correct me when I use the wrong terms.
I am really trying to figure out if this design is correct and what it actually does. I got the gist of how non-inverting configurations work, but I'm not sure how the input sine signal is transmitted.
First there's the input voltage at 3.3 V that gets divided evenly, so at Pin 3 (non-inverting input) there should be 1.6 V. I read that through a feedback loop the voltage at both inputs (inverting/Pin 2 and non-inverting/Pin 3) should be the same (1.6 V). Therefore there should be a gain of 11 (with R3 and R4) at output 1 right? I am able to measure the 1.6 V with a multimeter, but at the loudspeaker outputs the voltage seems to drop with time (probably because of the capacitors?).
I'm slightly more confused at what's going on at pin 5-7 because I don't understand how the sine signal is transmitted. I don't know what voltage there is at the non-inverting Pin 5, is it the voltage from the sine signal? Shouldn't it also get 3.3 V like Pin 3? When I try to measure it with a multimeter, there's little to no voltage and I can't seem to power the loudspeaker. I think it's because the sine wave measures only about 150 mV.
The op amps:
Currently I'm using the AD8616 because of its high output current. The data sheet reads 150 mA at 5 V, so I'm thinking of switching the 3.3 V input to 5 V because of the loudspeakers high impedance of 50 ohms, so it can get more power.
I'm sorry if I'm all over the place, I'm stuck at what I should do or switch up to get the loudspeaker to work.