Hi --
I set up a circuit (attached) to explore the 2N3904 transistor. When I change the 100K Pot I get the expected results (my LED goes from dim to bright as the POT goes from high to low resistance). I see that the current through R1 is changing as expected but what I don't understand is why is the voltage across R1 changing? Is that expected? I was expecting only the current to change as the transistor changed its saturation amount?
My readings:
IB 1 mA, IR1 25 mA, VR1 5.6 V, Transistor Saturated, LED bright
IB 24 uA, IR1 3.7 mA, VR1 0.8V, Transistor Not Saturated, LED dim
So you see above that the transistor is doing what I expect to the current and also the LED does change brightness as expected -- but why does the VR1 change? I realize this must be expected but I can't see why from looking at the literature so if someone can explain (or point to online source) it would be greatly appreciated!
Thank you!
I set up a circuit (attached) to explore the 2N3904 transistor. When I change the 100K Pot I get the expected results (my LED goes from dim to bright as the POT goes from high to low resistance). I see that the current through R1 is changing as expected but what I don't understand is why is the voltage across R1 changing? Is that expected? I was expecting only the current to change as the transistor changed its saturation amount?
My readings:
IB 1 mA, IR1 25 mA, VR1 5.6 V, Transistor Saturated, LED bright
IB 24 uA, IR1 3.7 mA, VR1 0.8V, Transistor Not Saturated, LED dim
So you see above that the transistor is doing what I expect to the current and also the LED does change brightness as expected -- but why does the VR1 change? I realize this must be expected but I can't see why from looking at the literature so if someone can explain (or point to online source) it would be greatly appreciated!
Thank you!
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