I need to trigger a speaker if my input voltage is higher than 0.6 V, otherwise the speaker must not be triggered. That's the reason I'm using an AMPOP Comparator:
and, as far as I know, the voltage Vout should be:
$$ V_{\text{out}} = \begin{cases} V_{\text{S}+} & \text{if } V_1 > V_2, \\ V_{\text{S}-} & \text{if } V_1 < V_2, \\ 0 & \text{if } V_1 = V_2\end{cases}$$
But when I simulate my circuit, my output voltage is not Vs+ or Vs-. There is a loss in voltage and you can check all voltages on the following image.
V1 = 1 V and V2 = 0.6 V, Vout = 13.011, but Vs+ = 15 V;
V1 = 0.2 V and V2 = 0.6, Vout = 1.9889, but Vs- = 0 V.
I need Vout near 15 V (and 0 V if V1 < V2). It doesn't have to be exactly 15 volts, but near it. Am I doing something wrong? Is there any way to do it without another amplifier after the output? I'm beginner sorry if I misunderstood something.
BTW, if you know an easier way to trigger the speaker, tell me 😉
Best Answer
Do you even need +15V to -15V output???
Power on the speaker is ~Vpeak^2/R, so for an 8 ohm coil this system will blast out 15^2/8 ~= 28 Watts, which is pretty loud. Also placing DC current through a speaker is bad for it.
If you wanna stick with this design: you're going to need a Comparator with Rail-Rail operation, and even then that only gets you to Vdd-0.3V and Vss+0.3V . Check to see if this suits your needs. Since you are also driving a speaker, use Ohm's law on the speaker impedance to figure out how much current you're gonna need. An 8 ohm speaker will need at least a 2 Amp power supply for both +15 V and -15V. Best bet is to drive the system with +-18V 3A Rails. Find a comparator that can handle +-15V outputs, and get an output buffer that can handle 2 Amps both ways.