Sunday, 13 December 2015

high pass filter - What is the purpose of the 250uF capacitor in the LM386 circuit?



The basic amplification schematics shown in the LM386 datasheet shows a 250 uF capacitor in series with the output. I don't have any 250 uF, but I do have plenty of 470uF. If I understand correctly, is this capacitor used as a high pass filter, so should I be able to use a 470 uF instead of a 250 uF?


Also, is the resistor (10 ohm) and capacitor (0.05 uF) going to ground a low pass filter?



Answer



Yes, 470uF will work fine, it will just extend the bass response somewhat. It's a coupling capacitor (or a blocking capacitor, to block DC, if you prefer).


The 10R + 50nF is a "Zobel Network", intended to cancel out the reactive portion of the speaker impedance.


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