# What is Thermal Voltage?

Sure, let me help you understand the concept of thermal voltage - a term commonly used in semiconductor physics and engineering.

Thermal voltage is the amount of potential difference or voltage that is generated within a semiconductor junction due to temperature variation.

This principle is at the heart of the operation of a wide range of electronic devices including diodes and transistors.

## Thermal Voltage Formula

The formula to calculate thermal voltage (V_T) is given by:

`V_T = k*T/q`

Where,

• V_T is the thermal voltage

• k is the Boltzmann constant, which is approximately 1.38064852 × 10^-23 m² kg s⁻² K⁻¹

• T is the absolute temperature in Kelvin

• q is the charge of an electron, approximately 1.60217662 × 10^-19 coulombs

### Calculate Thermal Voltage at 300K

Now, using this formula, we can calculate the thermal voltage at room temperature, which is typically taken as 300 Kelvin.

Plugging in the values for Boltzmann's constant and the charge of an electron, we get:

V_T = (1.38064852 × 10^-23 m² kg s⁻² K⁻¹ * 300 K) / (1.60217662 × 10^-19 C)

Solving this, we get a value of approximately 25.85 millivolts (mV).

## How is thermal voltage produced?

Thermal voltage is produced due to the thermal energy provided to the charge carriers (electrons and holes) in a semiconductor material.

As the temperature increases, the thermal energy causes more charge carriers to cross the junction, creating a potential difference or voltage across the junction.

This phenomenon is directly related to the thermally activated diffusion of these charge carriers and is mathematically described by the Boltzmann factor, which is why it's also called Boltzmann voltage.

## Common Applications of Thermal Voltage

Common applications of thermal voltage principles are found in semiconductor devices, where it is a critical parameter in the operation of devices such as diodes, transistors, and integrated circuits.

Its most significant role is in the current-voltage characteristic of a diode, a principle captured by the Shockley diode equation.

### Main advantage of Thermal Voltage

The main advantage of understanding and applying thermal voltage is that it allows us to manipulate electronic devices in a way that is sensitive to temperature changes.

This has been key to the development of temperature sensors and various forms of temperature-dependent electronic switches.

### Disadvantage of Thermal Voltage

On the flip side, the main disadvantage or challenge with thermal voltage is that it introduces a temperature dependence into electronic devices.

This means that the behavior of these devices can change with temperature, which can be problematic in environments with significant temperature fluctuations.

It's also worth noting that thermal voltage is quite small, which can limit its direct applications.

Overall, the concept of thermal voltage is a fundamental one in the field of semiconductor physics and electronics, playing a vital role in understanding and designing many of the electronic devices we use in our everyday lives.

## Replies

• Jeffrey Arulraj
Thermal Voltage is the Voltage developed due to increase in temperature

We know that electrons get excited due to heat energy given to the semi conductor. This is why thermal voltage is generated in the semi conductor.

Heat energy is produced a lot due to the presence of comparatively higher resistance in the semi conductor and so we can't neglect thermal voltage any time
• Ahsanul haque
In semiconductors, the relationship between the flow of electrical current and electrostatic potential across a p-n junction depends on a characteristic voltage called the thermal voltage.Thermal Voltage increase electron motion that's why raise semiconductors conducting efficiency.
• Void Runner
The thermal voltage is simply there to ensure that the laws of (chemical) thermodynamics are followed inside a semiconductor device. It is basically the adjustment applied when nonequilibrium condition occurs (i.e. external temperature causing energy injection to the carriers). I cannot go any further than this without getting into hard core physics, but you will have to take this from me as the answer 😀
• ambrish gautam
Thermal voltage (Vt) is voltage that controlled the motion of electrons(current) in the influence of temperature across the p-n junction. vt=T/11600 where T should be in "k"
shows that if there is large variation in temperature cause small change in thermal voltage. this equation is also shows the relation between electric current and electric potential difference across the p-n junction.

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