Tweet
Hola,
So I'm back to playing with MOSFETs again. Specifically the LND150 (http://www.supertex.com/pdf/datasheets/LND150.pdf). What a cool little piece of silicon this is, but alas, I have a question regarding gate to source breakdown voltage (G/S BDV).
Conceptually I understand G/S BDV. If the gate is seperated from the source by more than some voltage (20v in the case of the LND150), the MOSFET can be damaged/die. Cool, makes sense, however, doesn't the source follow the gate more-or-less exactly? So how could the gate separate from the source by more than even the slightest voltage except for screwy bias?
The reason I'm asking is that often in schematics I've seen back to back series zener diodes between the gate and source. The reason usually given is that if the input signal to the gate exceeds the G/S BDV, the MOSFET can be damaged. But since the source follows the gate, I don't see how these zeners really do anything, but since I see them often, I'm assuming I'm missing something.
So I'm back to playing with MOSFETs again. Specifically the LND150 (http://www.supertex.com/pdf/datasheets/LND150.pdf). What a cool little piece of silicon this is, but alas, I have a question regarding gate to source breakdown voltage (G/S BDV).
Conceptually I understand G/S BDV. If the gate is seperated from the source by more than some voltage (20v in the case of the LND150), the MOSFET can be damaged/die. Cool, makes sense, however, doesn't the source follow the gate more-or-less exactly? So how could the gate separate from the source by more than even the slightest voltage except for screwy bias?
The reason I'm asking is that often in schematics I've seen back to back series zener diodes between the gate and source. The reason usually given is that if the input signal to the gate exceeds the G/S BDV, the MOSFET can be damaged. But since the source follows the gate, I don't see how these zeners really do anything, but since I see them often, I'm assuming I'm missing something.
Comment