I have a circuit which does something not important, but it results in an output being normally low, and then on activation climbs to a little below Vcc. At the moment, it appears my Vcc is 1.8 V and the signal gets up to between 1.2 V and 1.4 V. I want to use this signal to control the gate of an n-channel MOSFET which is grounded on the source and has the drain tied to Vcc through a large resistive load.
The problem is the threshold voltage of the standard MOSFETs I have appears to be too high, and I have to raise Vcc to about 2.2 V in order to get the circuit to trigger the MOSFET correctly. Are there better MOSFETs for this situation or some other design idea that would work well and solve my problem?
BTW, the switching speed is not really a consideration... we're talking 1-200 Hz for frequency.
Application Note, see page 3. I was hoping I could just use their circuit exactly and just mess with the tuning component, but it doesn't seem to work at 1.8 V.