How to switch a large-V load with a P-channel mosfet and small-V unipolar clock?

[johnyradio]

I didn't say the mosfet was faster, I said using the driver would allow the mosfet to turn off fasterthan the circuit in one suggested in another post because it included a charge trap that would not allow a mosfet to turn off quickly. Using a driver insures you don't have a charge trap. The circuit I suggest I post 19 should be fast enough for your 400Hz frequency.

The only suggested circuit which doesn't include a driver is the zener configuration, you mean faster than that one?

Apologies, as my requirement is 20 kHz to 80 kHz clock (fixed). Plz see OP (original post) for improved description. Is post 19 still good for that?

Your post 19 appears to use N-channel mosfet, no? Need p-channel.

many thx

 

[rjenkinsgb]

The ltspice version using bipolar transistors would work fine with 3V logic, it just needs the last stage supply voltage to be somewhat higher than the logic supply voltage. 3V logic and 6V supply should work OK.

For extreme voltage or load current variations you would have to use different resistor values or possibly higher rated transistors but for smallish signals and up to 20V or so, just 1K resistors in R1 - R2 - R3 should still be fine.

FETs can result in less components, but you have to be extremely careful selecting appropriate devices where not much gate voltage is available (like for 3V logic) and the gate voltage needs limiting for high voltage use, above 15V or so.
Bipolar transistors are less critical.

 

[johnyradio]

The ltspice version using bipolar transistors would work fine with 3V logic, it just needs the last stage supply voltage to be somewhat higher than the logic supply voltage. 3V logic and 6V supply should work OK.

many thx. But what if i need freedom for load V to be lower or higher than clock V, with no change in components?

if that's too much trouble, don't worry about it