Driving higher voltages with p-type MOSFET

what I was looking for. Thanks John. > >Don --- My pleasure. :-) -- JF

could have just used an n-type MOSFET and controlled it directly with the MCU.

you start thinking about using a PNP to switch it, you run into the same problem.

Nothing will put the emitter voltage higher than the base, the B-C diode is plenty strong enough. puwer up isnt going to be crazy. But you've got a base current problem when you try to turn the transistor on.

what I was looking for. Thanks John. > >Don --- My pleasure. :-) -- JF

could have just used an n-type MOSFET and controlled it directly with the MCU.

you start thinking about using a PNP to switch it, you run into the same problem.

Oops! Needs a base or emitter resistor?

Grant.

what I was looking for. Thanks John. > >Don --- My pleasure. :-) -- JF

could have just used an n-type MOSFET and controlled it directly with the MCU.

as you start thinking about using a PNP to switch it, you run into the same problem.

For you, a Base R would be the simplest approach..

driving the gate directly from a mictrocontroller that uses +5 and ground. The problem is that I need +24 and +19. I looked into "high voltage level translators", but they have been discontinued or are a non-stock item.

Simpler:

uP gnd port

where the uP port is active low, 3.3v logic.

driving the gate directly from a mictrocontroller that uses +5 and ground. The problem is that I need +24 and +19. I looked into "high voltage level translators", but they have been discontinued or are a non-stock item.

driving the gate directly from a mictrocontroller that uses +5 and ground. The problem is that I need +24 and +19. I looked into "high voltage level translators", but they have been discontinued or are a non-stock item.

I think he can handle that difference. 5 volt logic is getting pretty rare these days!

with R2 in the emitter of

Why impossible? This circuit allows any desired drop across R1, up until the NPN saturates. With a 24 volt supply, 5 or maybe 10 volts across R1 is easy.

The nice thing about this topology, besides the simplicity, is that the NPN is a constant current sink, so the drive to the upper pnp/pfet is independent of changes in the +24 supply.

To flip the control polarity, just do this:

The R1/R2 math is the same, but the uP port can be wimpier, since it doesn't have to sink the drive up into R1.

I'm driving the gate directly from a mictrocontroller that uses +5 and ground. The problem is that I need +24 and +19. I looked into "high voltage level translators", but they have been discontinued or are a non-stock item.

Thanks John.

Don