PWM controls current or voltage?
Ohm's Law is a law of nature and it's always true.
For example, with less than 0.5V across a diode junction (or the base-emitter junction of a transistor) the resistance is low and very little current flows.
I read a lot about transistor in the internet but I still have a question. I know the transistor amplifies the current in the base to an equivalent amount of current in the collector/emitter. As far as I know I control the voltage across the base with an Arduino using analogWrite(pin,0), analogWrite(pin,100)..., analogWrite(pin,255). But you see, I am controlling the voltage not the current! So how does changing the voltage across the the base am I also changing the current? I am not using any resistor in my base, I connected it directly to my arduino PWN pin. But when I change the voltag across the base I can see a very different current coming out from the transistor so probably changing the voltage in the base is someway changing the current in the base which changes the current in the output of the transistor.
If I connect and LED to the output of the transistor it changes the brightness when I send a 100, 150... 255 PWM.