Author Topic: How to switch a large-V load with a P-channel mosfet and small-V unipolar clock?  (Read 317 times)

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Offline johnyradio

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i can switch the supply voltage with a unipolar clock, if the clock has the same peak V as the source supply



but if i make the source V higher than the gate V, i get a flat line output.



How to switch a high-V load with a low-V gate, on a P-channel mosfet? Prefer single-stage

Thx
« Last Edit: October 13, 2018, 06:19:52 am by johnyradio »
 

Online exe

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Do you need a high-side or low-side switching? If low-side, just put load at the drain.

If high-side, I'd propose an additional bjt as level shifter. Something like this: https://www.chegg.com/homework-help/questions-and-answers/bjts-often-used-level-shifting-changing-voltages-microcontroller-outputs-control-parts-cir-q21548315 or this: https://www.luisllamas.es/wp-content/uploads/2016/07/arduino-transistor-driver-bjt-mosfet.png . AFAIK, The Art of Electronics has a paragraph on this.

Just be sure to thoroughly test it: mosfet should open/close reasonably fast, and it should be fully open. Also gate voltage should not exceed absolute maximum ratings (clamp it to 10-15V with a zener to be sure, if needed).
 


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