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does the SKY130 process support depletion-mode fet?
# sky130
p
does the SKY130 process support depletion-mode fet?
h
There is an NMOS NVT available which has a Vth ~ 0V (not exactly what you are looking for but close). There is no MOS-FET available with a negative Vth (NMOS) and positive Vth (PMOS), respectively.
p
neat, is that 
sky130_fd_pr__nfet_05v0_nvt
?
I didn't realize there was something between the enhanced and depleted variant.
the cross section doesn't look that different from a regular FET
is the only difference in the size?
oh it doesn't have that 
Vt adjust implants
thingy too!
that makes sense if the only difference is the Vt 🙂
image.png
h
Exactly, the difference is the channel implant (under the gate). This influences the Vth. The “natural Vth” (NVT) sit without additional implant in the well/substrate.
p
Does it trigger on Vg >= Vs or 0 <= Vg <= Vs ?
(I assumed the former, but I wasn't 100% clear after reading https://en.wikipedia.org/wiki/Native_transistor)
h
Thanks for Wiki link on the native MOS-FET, didn’t know that one exists 🙂
p
those wikipedia pages are suprisingly good (and accessible!)
I tried to simulate the native fet in an inverter circuit https://gist.github.com/proppy/dd2352e210b58e6c4b0c9deb84aef579 but it looks a bit weird (i.e the voltage doesn't go back to 0)
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