How to switch a 12v circuit with a 4V pulse generator

[Damian666]

Hello All,

I have a pulse generator (1MHz max) that outputs about 4v and I need to turn on a turn on the power to a 12V circuit (about 1.5A max), I am after the simplest circuit to do the job. I was hoping to use a simple MOS switch - the problem I have is the MOS transistors I am familiar with require about 10V VGS . Any advice would be appreciated!

[pebe]

The gate capacitance of a FET may be a bit high to drive directly with 4V at 1MHz. I would recitify it with a small diode feeding into a 100K and 1nF in parallel. You an then use the resulting DC to drive an NPN transistor to feed Q1.

[Damian666]

Thanks for the observation, I will certainly do some simulations to look at this. My 1MHz was probably more than required - I anticipate the maximum frequency to be below 100KHz.

Any suggestions for a FET I could use – I need to ensure that the NPN pass transistor switches off.