In the context of diodes, "turn-on voltage" refers to the minimum voltage required to make the diode conduct current in the forward direction. Diodes are semiconductor devices that allow current to flow in one direction while blocking it in the opposite direction. When a positive voltage is applied to the anode (the positive terminal) with respect to the cathode (the negative terminal), the diode is said to be forward-biased.
In the reverse direction, a diode acts as an insulator, preventing any significant current flow. However, when the forward-bias voltage exceeds a certain threshold, known as the turn-on voltage or forward voltage drop, the diode starts conducting current and behaves like a closed switch.
The turn-on voltage for different diode types varies. For standard silicon diodes, the typical turn-on voltage is around 0.6 to 0.7 volts, while for Schottky diodes, it can be lower, around 0.2 to 0.4 volts. Other specialized diodes might have different turn-on voltage characteristics.
It's important to note that once the diode is conducting, the voltage drop across it remains relatively constant over a wide range of forward currents. This characteristic allows diodes to be used in various applications, such as rectifiers, voltage regulators, and signal demodulation circuits, where their ability to conduct current in one direction efficiently is essential.