Why no collector current?


Joined Nov 30, 2010
If the meter on the right was correct, there would be 12 volts across the LED and the 1 ohm resistor...but it isn't correct. If you really built this circuit, the resistor and LED would smoke instantly by trying to survive over 9 amps. If this happened, all the readings become correct because the LED melted and no current passes.

Sometimes you just can't believe a simulator.

Thread Starter


Joined Oct 6, 2011
Ah, its my mistake the simulator didnt connect it to battery terminal. It didnt consider another ground terminal, so i connected the right ammeter to battery grounded terminal and it worked!!.



Joined Mar 31, 2012
Don't know why I _{c} collector current is zero. I have got these reading in ammeter and voltmeter.
Are you sure the two grounds symbols represent the same node? Sometimes symbols for global node connections let you specify a different global node in order to support multiple supplies and multiple grounds. But, usually, the ground symbol shown like that one will default to node 0, which is the simulator's reference node (for most, if not all, SPICE-based simulators).


Joined Dec 20, 2007
The 1 ohm resistor value is much too low. It causes the current in the LED and collector-emitter of the transistor to be much higher than their maximum allowed currents.
This makes the transistor and LED much hotter than their maximum allowed temperature.
Then they burn out.

The transistor has 1V from base to emitter with no resistor to limit the current which which also probably burn out the transistor.