Achieving higher current at the lowside MOSFET to pulse LED

bjtledmosfetpulsetotem-pole

I have attached the following circuits which i have been developing overtime.

The OBJECTIVE is to get as high as possible a current at the gate of the MOSFET (VF1) to achieve faster pulse times of the LED.

My questions are:

-if there is any way to get higher currents at the MOSFET gate closest to the LED

-I am having trouble getting a higher voltage drop at the LED (VF2), adjusting the supply voltage VS1 has not contributed to increasing voltage across the LED

-the first circuit uses two mosfets and the second circuit uses an NPN/PNP BJT totem configuration to get higher current at the gate of the power MOSFET. Which of the two configurations should i pursue if my goal is to get faster switching at the MOSFET near the LED?

The circuit file is attached as well as the transient graphs. Any help/advice is welcome.enter image description here

enter image description here

Best Answer

Method 1 has no gate pull down for the right hand MOSFET (Q2) so never turn it off properly.
The circuit could be modified to work properly, but the second circuit is easy and works well (when the error noted below is fixed).

In the lower circuit the PNP transistor should be inverted with collector to ground and emitter to output. The FET gate peak current is set by transistor capability and RS10. Depending on speed really required RS10 can be adjusted but usually 500 mA to 1A peak is adequate. What switching frequency do you require?

Related Topic