Make mosfet turn on higher than threshold

[throbscottle]

Is there a way I can get a mosfet to switch at a voltage higher than it's threshold voltage? I tried the scheme attached, but wondered if there's a better way. I'd be using a low voltage zener (eg, 3.3v) rather than a signal diode, but there isn't one in LTSpice. I want the mosfet to switch high up the capacitor's charging slope, but I want to use the voltage at the cap as well so it can't be pulled down too much.

thanks in advance

 

[audioguru]

The threshold voltage of a Mosfet is different for each one even if they have the same part number. For the 2N7002 Mosfet the threshold voltage is anywhere from 1.0V to 2.5V when it barely begins to conduct only 0.25mA.

 

[crutschow]

If you want to have a precise trip point as to where the MOSFET switches, you'd be best off using a comparator such as an LM339.

 

[throbscottle]

Hmmm, I'll take that as a "no" then. The aim of this was to replace two switches, one of which is always pressed (effectively SPDT), with one switch and a transistor, but then I realised I needed to catch the brief "in-between" state where neither switch is pressed since either switch can generate a pulse via the same circuit. (The version I attached creates enough of a gap) Think I should just go back to using two switches rather than start adding more components.

As always, thanks guys