1. What is Resistor Thermal Noise?

Resistor thermal noise, also known as Johnson-Nyquist noise, is the electronic noise generated by the thermal agitation of charge carriers (usually electrons) inside an electrical conductor at equilibrium. It's present in all resistors regardless of the applied voltage.

2. How Does the Calculator Work?

The calculator uses the thermal noise equation:

Where:

• \( V_n \) — Thermal noise voltage (V)
• \( k \) — Boltzmann's constant (1.380649 × 10⁻²³ J/K)
• \( T \) — Absolute temperature (K)
• \( R \) — Resistance (Ω)
• \( \Delta f \) — Bandwidth (Hz)

Explanation: The noise voltage increases with higher resistance, temperature, and bandwidth. It's independent of the resistor's material composition.

3. Importance of Thermal Noise Calculation

Details: Understanding thermal noise is crucial for designing sensitive electronic circuits, especially in audio equipment, radio receivers, and measurement systems where small signals need to be detected.

4. Using the Calculator

Tips: Enter resistance in ohms, temperature in kelvins (293K = 20°C, 300K = 27°C), and bandwidth in hertz. All values must be positive.

5. Frequently Asked Questions (FAQ)

Q1: Does thermal noise depend on the resistor type?
A: No, thermal noise is fundamental to all resistors regardless of their composition (carbon, metal film, etc.).

Q2: How does temperature affect thermal noise?
A: Noise voltage increases with the square root of absolute temperature. Doubling temperature increases noise by about 41%.

Q3: What's the relationship between bandwidth and noise?
A: Noise voltage increases with the square root of bandwidth. A 4x bandwidth increase doubles the noise.

Q4: Can thermal noise be eliminated?
A: No, it's fundamental to resistors at finite temperature. Cooling can reduce it, but never to zero.

Q5: How does this relate to signal-to-noise ratio?
A: Thermal noise sets the fundamental limit to the minimum detectable signal in electronic circuits.