I have been dealing with some project in which I have some requirements to accomplish. For now, I am dealing with the first part and a quick story is,
I have to generate a sine wave at a certain frequency and then convert that signal into sound via using an 8 ohm speaker.
At least 1 W of power on the speaker.
Adjustable amplitude of the sine wave input of the speaker.
So what did I do:
I am using a wien-bridge oscillator circuit which looks like this to obtain the sinusoidal waveform. And what I get is a nice 16 Vpp (I assume 2 Vpp loss can be considered as normal) sinusoidal-ish waveform while no load is connected to the output of the opAmp. However, when the switch is being closed, i.e 8 ohm load(my speaker in this case) is connected to the opAmp's output, then the voltage on the speaker dramatically drops to 0(nearly 0) volts.
Now, If I did not do the math wrong, I need at least 4 Vpp on the speaker to reach required power rating. After all these, my need reduces to being able to have an adjustable 8 Vpp to 4 Vpp load voltage.
So, how should I proceed? I have thought of using a voltge divider network at the output with a potentiometer and a fixed resistor to tune the output voltage but I don't know that works, or if that can work then how should I arrange the values of the resistor and potentiometer so that I can safely drive an 8 ohm speaker.
p.s: Using job-specific IC's which will bypass design steps and give directly the desired outcomes are not allowed.
Mosfets, Bjts, Capacitors, Resistors, Potentiometers, DC batteries, opAmps, 8 ohms speaker, Switch, button, Wire(needed to write after some brutal comments..)