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Why does a MOSFET gate need a pull down?
The resistor can/should be relatively high valued compared to your input resistor to prevent excessive voltage drop when you have it set as a high input. You only have to drain the inherent capacitance on the MOSFET gate when you’re pulling it low so even at a high resistance to ground the RC time constant is usually relatively short.
Which is the threshold to turn off a MOSFET?
Fun fact, Vgs is the threshold to turn-off a MOSFET, not to turn it on. At first, this might seem backward. But, consider that the Vgs threshold has a range. The range defines the voltages where the FET transitions between “on” and “off.”
Do you need to know the resistor value for MOSFET?
Of course any time a resistor is shown in a schematic, people get worried about what complicated formula is needed to determine its value. For slow switching applications, like below 10 kHz, the resistor value doesn’t matter. Something in the 100 to 1000 ohm range is fine.
Which is more complicated a MOSFET or a switch?
Even though transistors get used for switching applications, they are much more complicated than a switch. In the case of MOSFETs, they have three regions you need to understand: cut-off, linear and saturation. In the cut-off region, there is no current flowing between the drain and source.
What kind of resistor do I need for MOSFET?
Series resistor between Output pin and gate of MOSFET: The frequency on the gate-input will be not higher than approximately 220Hz, i.e. no high-frequency PWM. ATtiny26, DC current per I/O pin: 40mA (max.)
Can a FET have a low pull up resistor?
The on-resistance of a FET can be very low, even as low as a few mΩs for high current ones, but let’s take an average FET with a 1 Ω on-resistance, and a 10 kΩ pull-up resistor. Let’s say V S = 5 V.
Why is your too high in a MOSFET?
The leakage current is the reason why you shouldn’t choose R too high. If R would be 1 MΩ then the voltage drop would be 1 V and that may be too much. So it works with the resistor. What if we omit it?