Wednesday, 1 October 2014

transistors - LED on the collector without a base limiting resistor


am a beginner trying to understand transistors. I am using a npn transistor.


I have a 6V battery.



The base and collector are connected to 6V Emitter has the load (LED + 100ohm resistor) to the ground. Current passes and the LED lights up. I understand, it is in saturation mode. With or without a base resistor.


Case 2: The base is connected to 6V. The collector has the load (LED + 100ohm resistor) connected to 6V as well. Emitter is connected to the ground. The LED does not light up when powered.


Case 3: Further to Case 2: I use a 1K resistance with the base and the LED lights up.


Why does not the LED light up in case 2?


This seems similar to Emitter Follower LED Circuit - LED in Collector, Resistor in Emitter, but I did not get the concept.


Thanks.




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