Old thread but want to ask - I see several versions of the amplifier LM386 at DigiKey for different wattages, 325mw, 700mw, and 1W. Does it matter for this circuit? Since it wasn't specified, guessing not. Can an approximate wattage be calculated without using something like LT Spice?
This Week on the Breadboard: The Bloody Germanium Overdrive
- Thread starter Chuck D. Bones
- Start date
Chuck D. Bones
Circuit Wizard
We can do a quick cocktail napkin calculation to get into the ballpark.
Maximum output swing is around 8Vp-p. Assuming a square wave, that works out to 4Vrms. There is a 560Ω series resistor (R15). Output power is Pout = 4^2/560 = 29mW delivered to R15. This is pretty much the worst case situation: output shorted. If we look at the datasheet device dissipation vs. output power, the 9V curve indicated that at 29mW output, the device dissipation is around 350mW and most of that is quiescent dissipation (the power dissipated when the output power is zero). The DIP packages (N suffix) are all rated for 1.25W dissipation. We have plenty of margin and this was a pessimistic calculation. The only time we care about the part no. suffix is when we want to run on a higher rail voltage (N-4 suffix). The SMD parts have a lower max dissipation limit, but they would still have positive margin.
Maximum output swing is around 8Vp-p. Assuming a square wave, that works out to 4Vrms. There is a 560Ω series resistor (R15). Output power is Pout = 4^2/560 = 29mW delivered to R15. This is pretty much the worst case situation: output shorted. If we look at the datasheet device dissipation vs. output power, the 9V curve indicated that at 29mW output, the device dissipation is around 350mW and most of that is quiescent dissipation (the power dissipated when the output power is zero). The DIP packages (N suffix) are all rated for 1.25W dissipation. We have plenty of margin and this was a pessimistic calculation. The only time we care about the part no. suffix is when we want to run on a higher rail voltage (N-4 suffix). The SMD parts have a lower max dissipation limit, but they would still have positive margin.
bluedmc777
Well-known member
Supposed nobody made this it seems interesting!
z2amiller
Active member
I put together a layout for this over the weekend - I'll probably have it in my hands in a couple weeks when I get my next batch of stuff from JLC. If it sounds good, I'll share the gerbers with @Chuck D. Bones 's blessing.