The simple fade out/in switch circuit

Published:2011/7/7 20:54:00 Author:Seven | Keyword: fade out/in | From:SeekIC

The simple fade out/in switch circuit is shown in the figure, usually, the switch S is open, triodes VT1 and VT2 are both blocked, the lamp E is not glowing. When we need the lamp to light, just close S, the 220V AC current is turned into an impulse DC current after rectification, the capacitor C is charged by switch S and resistor R, which makes the voltage on C rise. Therefore, VT1 can acquire rising basic bias current through R2, so VT1 and VT2 are both turn into the amplifying state from the blocked, finally, they are fully conducted.



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