Electronic – High Side P channel mosfet with totempole driver + floating / voltage follower pull down


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

Best Answer

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.


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.