So in my notebook I have this circuit scheme for a NMOS static inverter:

enter image description here

Vi is the input
Vo is the output
VDD is the voltage source
It is obvious that the M2 MOSFET will never turn on. Is the circuit wrong? Is something missing?
Please help me find a way to correct this STATIC NMOS Inverter.

  • 1
    \$\begingroup\$ Your circuit shows enhancement mode MOSFETs hence, your circuit will never work. If the upper MOSFET was a depletion mode MOSFET, it stands a chance. Maybe you didn't transcribe it from your book correctly? \$\endgroup\$
    – Andy aka
    Jan 17 at 21:16
  • \$\begingroup\$ M2 should act as the so-called "dynamic load" (constant current source). \$\endgroup\$ Jan 17 at 21:43
  • \$\begingroup\$ @Andyaka indeed the M2 transistor is a depletion mode MOSFET. \$\endgroup\$
    – Kudor
    Jan 17 at 22:22
  • \$\begingroup\$ @Circuitfantasist I have understood that it needs to function as a dynamic load, but why was it designed this way (a not working way) in the notebook? \$\endgroup\$
    – Kudor
    Jan 17 at 22:24
  • \$\begingroup\$ @Kudor you've drawn it as an enhancement mode MOSFET. \$\endgroup\$
    – Andy aka
    Jan 17 at 22:30

1 Answer 1


It is very likely an internal schematic of an integrated circuit and as such it contains devices and connections which are not available as discrete solutions.
In this case, the M2 is also an N-channel MOSFET, but the substrate, which usually has its other end connected to the Source electrode, is not connected to Source but rather free-floating and connected to ground or zero point of the circuit, most likely to act as a constant current source.


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