| Electronics > Beginners |
| Capacitors don't work like I thought, please help me understand. |
| (1/6) > >> |
| gilligan:
Why does this work? http://tinyurl.com/y679uqr8 |
| jpanhalt:
What did/didn't you expect it to do? |
| PartialDischarge:
Not the kind of circuit you’d want to build but, the gate to source connection is also a capacitor, a small one. In a resistor divider, the large resistor takes most of the voltage, in a capacitive divider, the small cap takes most of it. The current through the large capacitor is going to be very small but enough to charge the gate up to nearly 5v. Id recommend you to watch this video which is somewhat related |
| Wimberleytech:
The voltage across a capacitor is V= 1/c (integral) i dt So you reset the capacitor so that it has zero volts across it (zero charge). In order for the voltage on the capacitor to change there must be a current to charge it according to the equation above. There IS NO CURRENT PATH. The input resistance of the mosfet is infinity. Since no current flows, the voltage across the cap never changes--remains zero volts. So the Vgs of the mosfet does not change either. Surprisingly, this is a useful concept--with a few additional components. |
| gilligan:
I always assumed that Caps blocked voltage. So when the switch was opened, after the cap drained then there would not be anything on the gate of the MOSFET. But it seems like this will just latch the MOSFET open and just run continuously even when removing supply to the Gate. |
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