1. What is Resistive Noise?

Resistive noise, also known as Johnson-Nyquist noise or thermal 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 and is proportional to temperature and resistance.

2. How Does the Calculator Work?

The calculator uses the resistive noise equation:

Where:

• \( V_n \) — Noise voltage (V)
• \( k \) — Boltzmann constant (1.380649 × 10⁻²³ J/K)
• \( T \) — Absolute temperature (K)
• \( R \) — Resistance (Ω)
• \( \Delta f \) — Bandwidth (Hz)

Explanation: The equation shows that noise voltage increases with higher temperature, resistance, and measurement bandwidth.

3. Importance of 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 temperature in Kelvin, resistance in Ohms, and bandwidth in Hertz. The calculator will output the noise voltage in nanovolts (nV).

5. Frequently Asked Questions (FAQ)

Q1: Does this noise depend on the resistor material?
A: No, thermal noise only depends on resistance, temperature, and bandwidth, not on the resistor's material composition.

Q2: How can I reduce thermal noise in my circuit?
A: You can reduce noise by lowering temperature, decreasing resistance, or limiting bandwidth to only what's necessary.

Q3: Is thermal noise the same as 1/f noise?
A: No, thermal noise is white noise (constant across frequencies) while 1/f noise increases at lower frequencies.

Q4: Does this apply to capacitors or inductors?
A: Only to the resistive component of these elements. Ideal capacitors and inductors don't generate thermal noise.

Q5: Why is the noise voltage so small?
A: The Boltzmann constant is very small, so noise voltages are typically in the microvolt or nanovolt range for common resistances and bandwidths.