Electrical – Simple voltage inverter with mosfet/bjt

bjtinvertermosfet

I want to build a simple voltage inverter, just using two diodes and two caps to get a source of negative voltage.

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The problem is, that my micro is running at 3.3V and I need at least -6V and about 10-15mA. I have a +8V rail availible in my circuit, so I need a way to use the 3.3V to switch the +8V. I tried simulating this in LTspice:
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But it did not work very well, and it has the problem that when the mosfet is open, it is just wasting power on R41. How to do this correctly? I think I need more than one mosfet/bjt…

Best Answer

You only have 3 active switches ( 1 FET 2 diodes and a 100R resistor ) instead of 4.

enter image description here This is the ideal circuit. and ESR of switch and caps is key to your requirement with Load regulation error being 1V/@15mA = 67 Ohm The ESR of 3.3V 74ALSxxx drivers are 22~33 Ohm for example.

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