The following figure is a circuit diagram showing the use of a mosfet as a load switch.
Mosfet load switch circuit.
When mosfet is in cut off triode region it can work as switch.
Load switch options the many possible applications for load switches let the load switch manufacturers offer multiple load switch configurations.
A basic load switch such as the nx3p190 from nxp figure 3 resembles the circuit in figure 1 it has the p channel mosfet controlled by a level shifting and slew rate control circuit.
When the load is connected at the source side the vgs will needs to be higher in order to switch the mosfet.
Mosfet switching circuits consists of two main part mosfet works as per transistor and the on off control block.
Power amplifier display asic logic load switch load switch load switch load switch voltage source power management fig.
How much voltage do i need to turn on the mosfet.
The circuit to turn off elements is referred to as a load switch.
In the above circuit it is a very simple circuit for switching a resistive load such as a lamp or led.
Load switches are placed in series with the voltage source and the load.
Example load switch circuit p channel load switch on off control vin load the pass transistor is most commonly a mosfet either n channel or p channel that passes the voltage supply to.
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When the mosfet turns on inrush current irush flows to charge this capacitor.
The typical load switch shows in fig.
This inrush current is reduced by increasing the series gate resistor rgate.
This may be supplied by any 5v compatible logic circuit producing a pwm signal at a frequency in the high audio frequency range.
Now that we have hooked up sufficient voltage to the gate to turn on the transistor then we must supply voltage to our load on the source terminal of the transistor.
Mosfet passes the voltage supply to a specific load when the transistor is on.
Mosfet works in three regions cut off region triode region and saturation region.
In most of the cases n channel mosfets are preferred.
A load switch is comprised of two main elements.
The mosfet switch circuit load in this case is a 12v 36watt automotive headlamp bulb and the input to the mosfet switch will be a pulse width modulated logic level signal.
In example i have 12v dc with irf n channel type logic level mosfet and the load connected on the source side.
Generally large capacitor co for voltage stabilization is connected to the output side of the mosfet.
This also allows for the mosfet s gate drive or switching signal to be referenced to ground low side switching.
For an irf9640 mosfet 3v at the gate is more than sufficient to switch the mosfet on so that it conducts across from the source to the drain.
The pass transistor and the on off control block as shown in figure 1.
