I'm designing a very simple circuit which contains a microcontroller, an LM386 and a speaker.
I've previously asked a question:Help in designing a speaker driven by an LM386 and the answers helped me a lot. However, there are still some fine tuning I need to do in order to maximize the performance:
The speaker is 4-Ohm (as I measure using a voltmeter). I don't know it's rating (I persume 1W) LM386 can provide (typically,according to it's datasheet) 325mW.
Now, I just want to make sure the planning I'm doing is correct:
- The microcontroller produces 2.4v signal (under 20kHz)
- I multiply it by 0.05 (two resistors) and feed the amplifier with it
- (I'm using basic LM386 apllication;GAIN=20) the amplifier multiplies it by 20 so we're back to 2.4v
- I filter the signal with a simple RC circuit (30-Ohm,200nF, cutoff at 30kHz)
- so basically now I have 2.4v on 4 Ohm.
obviously, the LM386 cannot provide so much power! my questions are:
- what happens if I try to draw so much power from the LM386? will the signal be distorted? or simply less powerful?
- Am I doing the planning right? I mean, in order to draw 325mW I simply need to play around with the resistors until I drop about 1.3v on the speaker,is that correct?