The Thermal Noise Power Conversion Calculator determines the noise power generated by thermal agitation of electrons in a resistor or electronic system. This noise, also called Johnson-Nyquist noise, is fundamental and depends on temperature and bandwidth. The result helps RF and communication engineers estimate the noise floor of receivers and amplifiers.
Formula
Pn = 10 × log10((k × B × T) / (1 mW))
Constants
- k = 1.38064852 × 10⁻²³ (Boltzmann constant)
- 1 mW = 1 × 10⁻³ W
Formula Explanation
- T = Temperature in Kelvin (K). Room temperature is approximately 290 K.
- B = Bandwidth of the system in Hz, kHz, MHz, or GHz.
- Pn = Thermal noise power in dBm, representing the inherent noise level across the given bandwidth.
- The noise increases linearly with temperature and bandwidth, but the result is expressed logarithmically in dBm.
Uses of this calculator
- Estimating receiver noise floor in RF and communication systems.
- Evaluating system sensitivity and signal-to-noise ratio (SNR).
- Designing low-noise amplifiers and filters.
- Characterizing thermal effects on signal performance.
What is the thermal noise power at 290 K over a 1 MHz bandwidth?
Input: T = 290 K, B = 1 MHz
Output:
- Pn = 10 × log10((1.38 × 10⁻²³ × 1 × 10⁶ × 290) / 1 × 10⁻³)
- Pn = 10 × log10(4.002 × 10⁻¹⁵)
- Pn = 10 × (-14.398) = -143.98 dBm
- Thermal Noise Power ≈ -144 dBm