Electronic – Transistor PWM Generator (No ICs) for practical application

bjtmosfetpwmswitch-mode-power-supplytransistors

I want to produce a good quality PWM signal with transistors(BJTs, FETS, etc..). I do not want to use an IC at all(learning to use transistors properly). I'm currently using a BJT Astable Mutivibrator
enter image description here

@Source pin is a mistake I meant drain

As you can see the signal is fine until I attach the mosfet.

I've tried the configuration using 1N4148s to improve rise time, however due to the current limitations of the switching diode the signal isn't strong enough, I've tried various amplification techniques I found online, but the results were so horrible they weren't worth posting.
The DC-DC converter works like this, however it is not the subject of the question.

How can I stabilize this signal for practical general purpose use or is this an exercise in futility?

EDIT
To Newbies, DO NOT BUILD THIS!
If you want to build a boost converter from jellybean parts, use an NE555 and an OP-AMP or (better) comparator to regulate the voltage via the CV pin, even then there's a nasty ripple voltage. However the answer to the question is correct emitter follower(pushpull amp), etc was the best way to go. Oh and please don't use an autotransformer, it does lower the stress on your MOSFET, however the voltage isn't controllable without a switching regulator on the output end.(Which should probably be implemented in any case.
)

Best Answer

Add a buffer using complementary emitter-followers to drive the MOSFET gate as follows:

schematic

simulate this circuit – Schematic created using CircuitLab

This will greatly reduce the loading the MOSFET gate is causing on the collector output. At your ~100kHz frequency the MOSFET gate will be almost like a short.

Related Topic