Single-NPN driver for an N-channel MOSFET

Question

After years of neglect, I have just got back on track in my journey of learning electricity and electronics, and I am now considering the building of multiple projects to which MOSFET gate driver circuits are essential.

While browsing the internet for gate driver circuits that do not involve ICs, I came across this circuit where both the driving circuit and the power MOSFET are independently supplied with electricity, each with its own DC power source and ground.

The operation is very straightforward. A square-wave generator switches the NPN transistor labeled T4 on an off by feeding the signal through its base, while the N-MOSFET T3 is connected in an emitter-follower configuration. When T4 is on, current flows between T3's drain and source, supplying the light bulb B1 with power. Once T4 is off, T3's gate is discharged through R1, while the current between its drain and source grinds to a halt.

This circuit seems to work based on on the PROTO simulator app on Android.

1. What are the flaws present in this circuit?
2. If you think the driver circuit works, then what are its limitations?
3. How can you improve it, if need be?
4. If this driver works, does it support high-frequency applications?

Answer 1

The bulb should be in drain, not in source.
Using follower and 5 V signal generator will supply the gate with 4.3 V only (Vbe drop).
Not suitable for HF because of slow gate discharging through pull-down resistor (R3).
You must include a low-side transistor instead R3 to speed up discharging.

Using a driver below is a good way to start:

^{simulate this circuit – Schematic created using CircuitLab}