The voltage is there whether there is a resistor or not.R3 is there for voltage to develop across the resistor .
All MOSFET gates look like a capacitor.1) How do you know the MOSFET has a capacitor
We don't put it there, it's intrinsic to the MOSFET gate.2) why do we need to put the capacitor there( at the gate )
You must do that to change the gate voltage and turn the MOSFET off and on.3) why do we need to discharge the capacitor
The rule I follow for simulations is that "if it works" then it may work in the real circuit.but in simulation ,when its not there it works also
@crutschow Makes sens thanksThe voltage is there whether there is a resistor or not.
All MOSFET gates look like a capacitor.
We don't put it there, it's intrinsic to the MOSFET gate.
You must do that to change the gate voltage and turn the MOSFET off and on.
You can't change the voltage on a capacitor without charging or discharging it.
@Delta prime i would think that the opto coupler acts like a trigger for the MOSFET , but high currents don't actually pass through them, is n't it the case with my diagram ?Hello there. for kicks and giggles why is the mosfet there?
Optocoupler output stages are not designed for high load currents. Maximum current levels for Darlington outputs are around 150 mA, and 300 mA is typical for SCR and TRIAC outputs. When high load currents are to be switched, the optocoupler output stage is used as a trigger circuit for a high power device.
R3 is there for voltage to develop across the resistor .
@IrvingThat's true, because you're only putting about 8v on the gate with the 220ohm there, but the full 12v without it.
But it also shows you are not turning the MOSFET on hard enough AND its a rubbish MOSFET. That device has an ON-resistance of 4 - 5 ohms... not milliohms, OHMS!
View attachment 213912
A good MOSFET, say an IRLZ44, will have an ON-resistance of 25milliohms
View attachment 213913
The difference is you are probably losing 1 - 2 volts across the MOSFET, depending on the size of your motor. And that MOSFET is going to get very hot if you ask your motor to do any serious work.
A very good MOSFET eg IPP048N04N will have an ON-resistance of ~4milliohms
View attachment 213914
Hello there. for kicks and giggles why is the mosfet there?
Optocoupler output stages are not designed for high load currents. Maximum current levels for Darlington outputs are around 150 mA, and 300 mA is typical for SCR and TRIAC outputs. When high load currents are to be switched, the optocoupler output stage is used as a trigger circuit for a high power device.
R3 is there for voltage to develop across the resistor .
Im in france i order on site Like Rs and franelle but they take sometime to arrive..Where are you in the world and who do you normally order from?
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by Jake Hertz
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