MOSFET Threshold Voltage Calculator
Calculate MOSFET threshold voltage with body effect and semiconductor device parameters
Calculate MOSFET Threshold Voltage
Gate oxide capacitance per unit area
Acceptor doping concentration in substrate
Fermi potential at the surface
Operating temperature in Kelvin
Voltage between source and body (0 = no body effect)
Intrinsic carrier concentration at temperature T
Threshold Voltage Results
Primary Equation: VT₀ = √(2εSiqNA(2φF))/C₀ - 2φF
Body Effect: VT = VT₀ + γ(√(2φF + Vsb) - √(2φF))
Surface Potential (2φF): 0.400 V
Thermal Voltage (kT/q): 25.9 mV
Threshold Voltage Analysis
Example: Typical n-Type MOSFET
Device Parameters
Oxide Capacitance: 5 nF/cm² (typical gate oxide)
Substrate Doping: 1×10¹⁵ /cm³ (moderate doping)
Surface Potential: 0.2 V (calculated from doping)
Temperature: 300 K (room temperature)
Calculation Results
VT₀ = √(2×εSi×q×NA×(2φF))/C₀ - 2φF
With typical values: VT₀ ≈ 0.4 V
Body effect: VT = VT₀ + γ×√factor
Typical range: 0.7 - 1.0 V
Key Parameters
Threshold Voltage
Gate voltage needed to turn on MOSFET
Body Effect
Source-body voltage influence
Surface Potential
Fermi level at semiconductor surface
Oxide Capacitance
Gate insulator capacitance
Applications
MOSFET device modeling and simulation
Circuit design and analysis
Semiconductor process optimization
Low-power electronics design
Semiconductor physics education
SPICE model parameter extraction
Understanding MOSFET Threshold Voltage
What is Threshold Voltage?
The threshold voltage (VT) is the minimum gate-to-source voltage required to create a conducting channel between the source and drain of a MOSFET. It marks the transition point where the MOSFET switches from OFF (cutoff) to ON (conduction).
Physical Significance
- •Determines switching characteristics
- •Affects power consumption and speed
- •Depends on fabrication parameters
- •Temperature and voltage dependent
Threshold Voltage Equations
Without Body Effect:
VT₀ = √(2εSiqNA(2φF))/C₀ - 2φF
With Body Effect:
VT = VT₀ + γ(√(2φF + Vsb) - √(2φF))
εSi: Silicon permittivity
q: Elementary charge
NA: Substrate doping concentration
φF: Surface potential for inversion
C₀: Oxide capacitance per unit area
γ: Body effect coefficient
Vsb: Source-body voltage
Body Effect: When source and body are at different potentials, the threshold voltage increases due to additional depletion charge.