modified 10 years ago

HELP - Transistor switch

01:11:01

Why won't this circuit operate the way it should be? The cap starts charged (when sim. is started) then after pressing the button it won't charge back up to 9V.... why????

published 10 years ago

GingerKing

10 years ago

Its really simple. When you press the button current flows through the base of the NPN on the left. The NPN then sinks current from the base of the PNP. The PNP then sources current into the base of the NPN that originally started the entire process. You made a loop which maintains its active state once supplied power. Its really unstable to keep "off" in real life. Getting back to the capacitor question now. The cap will not charge because current would rather flow through the NPN thats now being supply a constant current than flow through the large resistor and the capacitor. Whats the point of this anyway?

GingerKing

10 years ago

Current flows through the base of the NPN on the right*

trk21

10 years ago

My coment

kaivanveldhoven

10 years ago

Ahh I get it now! Thanks!

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