Kapanadze Cousin - DALLY FREE ENERGY

[verpies]

What happens to your pulse width if you replace the load resistor with your toroid and increase the collector rail voltage from 12V to say 50v?.

Without the flyback diode across the winding on the toroid (and w/o a snubber), the HV flyback pulse from the winding will avalanche this 150V_CE BJT transistor, when it tries to open at the end of the pulse - most likely damaging it permanently.

[Hoppy]

with or without the flyback diode installed?

Regards Itsu

Compare both with and without diode.

Regards
Hoppy

[Black_Bird]

@hoppy

All the internal capacitances in a semiconductor decrease with increasing voltage. Operating your transistor at a lower voltage will increase output ( and also feedback ) capacitances, masking the real operation at 150 Volts power supply.

[itsu]

Itsu,

What happens to your pulse width if you replace the load resistor with your toroid and increase the collector rail voltage from 12V to say 50v?.

Hoppy, when i install the toroid (6 turns) in the collector line together with a 1 Ohm CSR (and a Schottky flyback diode across the 6 turns as its my last KT926A which i don't want to loose), and running 4.6Khz repetition frequency and on my max. pulse width of 765nS, then at 42V (max. of my PS) the transistor is fully open.

Regards Itsu

[verpies]

when I install the toroid (6 turns) in the collector line together with a 1 Ohm CSR (and a Schottky flyback diode across the 6 turns as its my last KT926A which i don't want to loose), and running 4.6Khz repetition frequency and on my max. pulse width of 765nS, then at 42V (max. of my PS) the transistor is fully open.

...and you confirmed this by observing the voltage across the emitter and collector or across the 1Ω CSR?  - was it 42V or 0V, respectively?

Do you drive the base of the KT926A with your MOSFET Driver's output, or with the 74HCT02's output ?

If it is the latter, then notice that Hoppy is driving the base of his transistor with two TTL gates in parallel, and you are driving the base with only one TTL gate.

PS

The 74ABT00 and 74ABT02 would be much more suitable for direct driving these KT925A transistors. 
ABT gates are faster than HCT, too.