[sdiy] Shutdown on chip-amp

[Neil Johnson]

Hi,

Big N-channel MOSFET (with low rDSon) in the GND line of the power amp 
circuit.  Drive the gate with a logic signal from the PIC.

Hope this helps,
Neil


On Monday, May 2, 2005, at 06:45  pm, Johannes Öberg wrote:

> Short version: I need to make a small mono power amplifier (probably a
> LM386) shut down into some sort of low-power mode when not used, and
> this will be controlled by a PIC. I'm a total newbie.
>
> Longer:
>
> I'm building a small batteryoperated door-bell out of an ISD2560
> (lofi-sampler-on-a-chip) and a PIC. I guess I could have saved on
> parts, but it's my own "design" so it's a bit of an overkill to get it
> working.
>
> Anyway, I'm trying to reduce the power consumption as much as
> possible. I'm using the PIC in shutdown mode with interrupt-on-change
> so it only draws power when you press the door bell button. The ISD
> has a built-in power saving mode.
>
> All this works so far.
>
> However, while the ISD can drive a speaker directly, it is way too
> quiet for my needs. Therefor I need to use an external amplifier. The
> only one with built-in power down mode I can find readily available is
> surface mount :-(
>
> I looked at the LM386, but how do I make it power down? Can I just put
> some kind of PIC operated switch on the voltage supply for the LM386?
> Which one would you recommend? It doesn't matter if it's expensive
> because this is going to be one-time quick-and-dirty fix.
>
> Also, unfortunately, I'm short on time, and only have access to parts
> from www.elfa.se (the only local electronics supply), aparts from the
> random stuff I have at home of course.
>
> BTW, the LM386 only gives out 325 mW. Is that enough? I have little
> idea about these things, I have a 1W radio somewhere that is awfully
> loud even at low pot settings, so that's why I figure 325mW would be
> enough. Am I way off?
>
> Thanks in advance.
>
>

--
Neil Johnson <http://www.njohnson.co.uk>