Contents
How is a low side MOSFET turned on?
In the low-side configuration, the load is connected between the drain and +V, while the source is connected to ground. Thus, the gate drive is referenced to ground. So by applying a voltage of >7V (for Power MOSFETs) or >4V (for Logic Level MOSFETs), the MOSFET can be fully turned on.
What should voltage be for MOSFET to be on?
When the MOSFET is on, the MOSFET source will be at a potential of +15V. To be on, the MOSFET must have +8V VGS minimum. So, if source is at +15V, the voltage at the gate with respect to ground must be at least +23V.
What’s the difference between high and low side switches?
The low-side switch is switching ground while the high-side switch is connecting the voltage supply. Generally in a circuit, you want to keep the ground connected and switch the power. One reason is that even when the transistor is fully turned on, there is still a small voltage drop across it.
Why is capacitor used to drive high side MOSFET?
When the high-side MOSFET is to be turned on/driven, the voltage on the capacitor is used to drive the high-side MOSFET. Thus the limitation of this method is quite obvious. A large enough capacitor should be used for storing the required energy/charge for keeping the high-side MOSFET on for the required time.
Can a MOSFET be driven by an external circuit?
This MOSFET cannot be driven by applying a voltage at its gate and drain. It needs an external circuit to turn ON. The MOSFET used in the circuit is IRF840 which requires a gate to source voltage (Vgs) or threshold voltage (Vth) in range from 10 to 12V to fully turn ON.
Which is the best high side drive for MOSFET?
And the lower the frequency of operation, the larger the required capacitance. The easiest way to drive a MOSFET using the boostrap based drive is to use a dedicated high side MOSFET driver. Some drivers come with just the high-side driver while many come with both high-side and low-side drivers.
What can cause a drain-source short in a FET?
That is actually a MOSFET. Drain-source shorts are the usual failure mode in MOSFETs and are usually caused by transients on the gate. $begingroup$ Thanks Leon. That’s what I was wondering, could a transient at the gate or something cause a S-D short.