Cao-Thong Tu
Guest
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Fred,
I think that the word coupling cap is more for AC coupling of signals. For example, if you have a resistive input impedance of 100kOhms, using a capacitor will make an AC coupling and we might therefore use the terminology of coupling cap.
A bypass cap is a cap you typically use to shunt sources and avoid AC current flowing into a particular path. For example, imagine a NPN with resistor in the emitter and a load resistor at the collector. At high frequency, you can add a shunt capacitor in parallel with the emitter resistor to increase the gain. Such a cap, deviates the current into the shunt capacitor instead of flowing into the resistor, and this is called "bypassing".
Regards,
Cao-Thong
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