mosfet and pulses

The gate capacitance of the power MOS transistors is generally large, requiring a large driving current to quickly charge the gate capacitor and make it conduct quickly. At the same time, a current relief circuit is also required so that it can quickly close. In addition, the gate driving voltage of the power MOS transistor is generally ± 15V (the back voltage can reliably ensure that it is not turned on), so if your signal is only ordinary 3.3V or 5V (the driving current is very small, a few mA), you need a dedicated high-power MOS transistor driving IC or circuit.


Joined Oct 7, 2019
There are several different types of Gate capacitance, to drive.
The G-S cap must be charged from 0V to +15V. (voltage depends on what type of MOSFET you are using)
There is a G-D cap that is more complex. In my case I have 800V on the Drain that must be discharged to 0V.
The Gate Driver must charge/discharge the total capacitance.


Joined Sep 9, 2010
Note that magnitude of the problem is related to the frequency of switching. Anything below 10KHz is fairly trivial. (That's not a hard number, just a practical approximation.) The higher the frequency, the higher proportion of the cycle time the MOSFET is in the switching region - the self-heating region - instead of fully on or off. So heat production goes up with frequency and thermal management becomes crucial, even with a good driver.


Joined Jun 17, 2014
ı want to drive a power mosfet with rectangular pulses. what are the problems and solutions?

The problems, some of them already pointed out, include the following.
1. Gate drive current, related to how fast the MOSFET has to switch on and off, and also the frequency. This may mean an asymmetrical drive current.
2. Gate voltage. Different MOSFETs have different turn on voltage levels, you might need a logic level MOSFET for example.
3. Drain to Source voltage rating, and Drain current rating. Both ratings must be high enough to work in your application.
4. EMF due to the switching of the MOSFET. You may have to slow it down if your app allows that, which also lowers the maximum spike voltage level.
5. The point to point wiring. The driver circuit ground (for example) must connect to the Source terminal of the MOSFET with a separate wire in order to keep ringing to a minimum and prevent the notorious on/off oscillation that could occur when the MOSFET switches on. The wiring should be as short as possible, and this means attention to the physical layout of the entire construction.
6. Depending on load, you may need a snubber circuit to protect the MOSFET.
7. Depending on load vs choice of MOSFET, you may have to use an external parallel diode in parallel to the drain and source. This keeps some of the power out of the MOSFET package which can lower the temperature of the MOSFET.

These are some of the problems, but the main point is that you have to specify what you want to do with this circuit first, or some specs on how you intend to have the MOSFET behave. For example, drain rise time and fall time, maximum switching speed, stuff like that. There's no good way to recommend a driver unless we know more about your application.
To see how different this can be...
In a high power MOSFET converter that runs at 100kHz you have to supply a driver current to each MOSFET that is high enough to get it to switch fast enough, and this usually means a special kind of IC chip made for that.
In a slow, low frequency pulsing circuit made to time something (perhaps) you may get away with a small 2N2222 transistor and a pullup resistor.
So we went from a special kind of IC chip to a common NPN transistor and resistor. That's how different the driver circuit can be depending on application.