I'm reading this (fascinating reading):
and I noticed the capacitor. What value is this, typically? Should it be electrolytic, ceramic, ???
I also noticed one end is black, and the other white. Is the black supposed to be the (-) terminal of the cap?
Thanks,
Michael
Since both input source and output load are referenced to ground, and the NPN follower produces an output voltage one diode drop more negative than the input voltage, I think the negative side of the electrolytic capacitor goes to the emitter. The value of the capacitor is set by the lowest frequency that you want amplified and the load resistance. By Xc=1/(2*pi*f*C), you want to solve for C that produces a Xc lower than the load resistance at minimum frequency, f.
For example, if the load resistance is 32 ohms and you want little voltage drop across the capacitor down to 20 Hz you might shoot for a Xc of something like 10 ohms (less than
1/4 of the total signal voltage dropped across the capacitor at 20 Hz).So rearranging,
C=1/(2*pi*f*Xc)=1/(2*pi*20*10)=0.0008F=800uF.
I would probably use something between 470uF or a 1000uF.
For audio and low resistance loads, you can see why electrolytics are so practical. A very low voltage capacitor can be used because there is only about 0.6 volts across it, in this circuit.
Ah, ok. Low voltage...
Thanks for the clarification
Michael
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