The MOSFET threshold voltage is the topic we discussing in this article, threshold voltage is an important electrical characteristic of field-effect transistor devices. 

At MOSFET threshold voltage is also called the gate to source voltage, we know there are different types of MOSFETs are available but the most important division will be in terms of its polarity basis that is N-channel and P-channel MOSFETs. In this article, we include threshold voltage values of these MOSFET types and an equation for the threshold voltage at MOSFETs.

MOSFET threshold voltage? 

The MOSFET threshold voltage is the gate voltage or gate to source voltage for which the device gets trigger started.

The threshold voltage will be indicated as VT or VTH.

MOSFET threshold voltage equation 

MOSFET threshold voltage equation

b =  kT/q 1n (NA/Ni)

 

NA = doping concentration 

Ni = intrinsic concentration 

k = Boltzmann’s constant 

εSi = permittivity of silicon 

Cox = gate oxide capacitance 

Cox =  εox/ tox

Vfb = ϕms – Qfc/ Cox

Qfc = fixed charges due to silicon oxides

Φms = difference between silicon subtract and gate material 

Or 

MOSFET threshold voltage equation

N channel MOSFET threshold voltage 

The threshold voltage of n-channel MOSFET is a +VE value, which is between 0.7 to 1.0v.

P channel MOSFET threshold voltage 

The threshold voltage at p-channel MOSFET is a –VE value, which is between -2.0 to -4.0v.

The threshold voltage of the MOSFET is dependent on the doping density of the MOSFET device.

P channel MOSFET threshold voltage
P channel MOSFET threshold voltage
  • The substrate doping vs threshold voltage graph shows the difference in threshold voltage of n-channel and P-channel MOSFETs.
  • The n-channel MOSFET increases towards +VE voltage values and the p-channel MOSFET decreases to –VE voltage value, due to the doping density.

2n7000 MOSFET threshold voltage 

The 2n7000 is an n-channel MOSFET, they have a 3v threshold voltage.

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