Device physicsMVP
Thermal voltage
The thermal voltage Vt = kT/q sets the scale of diode and transistor sub-threshold exponentials.
Inputs
Result
Enter values and calculate to see the result.
Interpretation
Enter a temperature.
Formula
Vt = kB · T / q
kB = Boltzmann constant, q = elementary charge.
Variables
| Symbol | Variable | Unit |
|---|---|---|
| Vt | Thermal voltage | V |
| kB | Boltzmann constant | J/K (1.381×10⁻²³) |
| T | Absolute temperature | K |
| q | Elementary charge | C (1.602×10⁻¹⁹) |
Assumptions & validity
This tool assumes:
- Exact definition; no approximation beyond the constants used.
Worked example
T = 27 °C (300.15 K).
Vt = kB·T/q ≈ 25.9 mV