Question about a simple transistor switch??

Thread Starter

samy555

Joined May 24, 2010
116
Hi

The first image shows the situation when the transistor works as a switch

In the second photo I connect D2, the result: LED is no longer shine
My question is why?

Thanks alot
 

tindel

Joined Sep 16, 2012
804
D2 probably has a lower forward bias voltage than the Q2 base-emitter voltage... Which is drawing all the current away from Q2 and doesn't allow the LED to illuminate
 
Top