Inverter constructed using LDMOS transistors


I have the following question: is it possible to construct an inverter using LDMOS transistors when HV power supply is equal to 30 V and maximum VGS for LDMOS transistors is 5 V? Moreover, lower MV domain is 5 V.

See the attachment for visualization – problem section.

I can do following solution – see the attachment (solution section). However, doing it means constant current consumption and problems to turn on PMOS (apply 25 V on its gate). PMOS is turned on through 5R resistor.

Do you know if it is possible to construct such an inverter?


LDMOS inverter - problem and possible bad(?) solution

Best Answer

What you are looking for is a level translator circuit.

The core of this picture is what you will looking for. There is no quiescent current.

enter image description here

This picture is snipped from EE-Times article here as it gives some good background.

I've implemented similar circuits lots of times. It can be used to also shift the negative rail too, but the circuit is flipped and the transistors inverted (PMOS for NMOS etc.). The catch is that you can only shift one rail at a time, i.e. first the bottom rail and then the top rail. Having an output inverter is useful as this circuit is sensitive to loading on the internal nodes of T5 and T7.

You need to recognize the key aspect of the circuit can be reduced to the following:


simulate this circuit – Schematic created using CircuitLab