Semiconductor Devices: Class B Power Amplifier Example

[@rudygomez6996]

18:05 does large capacitor need to be coupled with low output impedance because it helps slow down charge/discharge rate of capacitor?

[@ElectronicswithProfessorFiore]

You could look at it that way, but a more direct way is to notice that the cap forms a voltage divider with the load. The larger Xc is, the greater the loss across it, thus we want a small Xc (which means large C).

[@rudygomez6996]

@@ElectronicswithProfessorFiore i never thought about that. thank you that really helped

[@davidluther3955]

EXCELLENT PRESENTATION!HOW DO YOU CACULATE THE OUTPUT IMPEDANCE FOR THIS CIRCIUT?IS IT THE SAME AS THE COMMON COLLLECTOR?

[@ElectronicswithProfessorFiore]

Pretty much yes, because only one device is on at any given time. (Technically, it is common collector although the "resistance in the base" section is a bit more complicated than in a single stage CC.)

[@simonyoungglostog]

Great stuff! Thank you.

[@hordrist929]

Good evening: I have a question about the power supplies (I am a beginner so it might seem like a stupid one 😂) For me, the power supply must be able to furnish the power demanded by the load + the transistors. What happens if the power suplly cannot do so ? Does it limit the circuit or does it damage the power supply? If for exemple if I have a ±15 V 10VA transformer and an 8 ohm load

[@ElectronicswithProfessorFiore]

That depends on the design of the power supply. If it's overload protected, most likely what will happen is that the supply rails will droop and probably show excessive ripple and noise. The end result will be a distorted output. If the supply is not protected, then yes, you could damage the supply (and also produce distortion along the way). If you are designing your own, a 10 VA transformer would definitely be undersized for that voltage.

[@hordrist929]

@@ElectronicswithProfessorFiore thank you for this detailed answer ! I am indeed trying to make my own guitar amp 😁 No need for something very powerful for a first time, I will already be glad if I can get some sound out of it 😂

[@TerryMcKenna]

Thanks, this is really informative. My only problem is understanding fractions of units, having used metric for 60 years.

[@ElectronicswithProfessorFiore]

You're singing to the choir! Halves, quarters, and thirds are fine, but stuff like 7/16ths is just dumb to me. Unfortunately, that's the way we often do things in the USA- just ask any carpenter or plumber!