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This is my first post (been an avid user though as I usually find an answer to my questions... this time I cannot despite a few days of searching.

I've created a push pull gate drive circuit for a high side back to back mosfet circuit... and I have it working in circuitlab and prototype...

However, I would like to know how to create it so that the pull down part of the totempole only pulls the gate down to VCC - 6V... to allow driving of voltages much higher than max Vgs (which for my circuit is -/+20V).

I've got a transient diode in there at 18V.. but that will not work for sustained VCC > 20V. I've tried various configurations of different circuits but can't get anything to work!

any pointers much appreciated.

totempole driver

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  • \$\begingroup\$ It's easier to drive if you can put the mosfets on the low side of the load (connect VCC directly to the load and the switch mosfet between the negative of the load and GND), if that is possible in your implementation. \$\endgroup\$ – Damien Oct 8 '18 at 9:09
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A technique that I like is to use Q3 as a current source, rather than as a saturated switch. This allows it to function as a level shifter, and eliminates the need for the Zener diode.

schematic

simulate this circuit – Schematic created using CircuitLab

Adjust R2 as needed to reflect the actual values of clock voltage and collector current needed; adjust R1 to set the gate drive voltage. Keep an eye on the dissipation of Q3, which goes up as Vcc goes up.

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A charge pump is the solution, further you can change P to N MOSFET, like LTC4365, MIC5021, . But the charge pump won't let you such high frequency switching - 10kHz. You should use an isolated DC/DC converter instead.

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