I have an LED Controlled by a signal to its cathode. If I make the cathode Low, LED Glows, and if cathode is High, LED is OFF.
The voltage applied at LED Anode is always 12.5V.
I observed that, when I turn ON the LED,
Voltage at LED Cathode = 0V
Voltage at LED Anode = 2.1V
And, If the voltage at the cathode is made high,
Voltage at Anode = 12.5V
Voltage at Cathode = 11.2V
LED Doesnot glow.
My question is, in my second case, when the LED Doesnot glow, why is there a voltage difference between the LED Cathode and Anode?
I understand that in the second case, the voltage difference between the cathode and anode is not greater than the forward voltage of the diode which is why it is not glowing. But when it is not glowing, why is there a voltage difference between the anode and cathode?