Measurement methods and important indicators of noise voltage

Noise voltage in electronic systems refers to random voltage changes that occur during system operation. This change is mainly caused by factors such as thermal movement, charge movement inside the electronic device, and external interference. Although noise voltage cannot be completely eliminated, its impact on system performance can be reduced through appropriate design and control.

Noise voltage has the following important characteristics:

1. Randomness: Noise voltage is random and not predictable. Its size and shape depend largely on the characteristics of the noise sources present in the circuit or system.

2. Broadbandness: The fluctuation frequency range of noise voltage is usually very wide, from a few hertz to several gigahertz or even higher. Therefore, noise characteristics across the entire frequency range need to be considered when designing electronic systems.

3. Statistical: Noise voltage can be described and analyzed using statistical methods. Common statistical indicators include root mean square (RMS), power spectral density (PSD), and autocorrelation functions.

There are many sources of noise voltage, mainly including the following aspects:

1. Thermal noise: caused by thermal movement inside electronic devices. According to the principle of thermal energy balance, the higher the temperature, the greater the noise voltage. Thermal noise mainly comes from resistors, transistors, diodes and other components.

2. Funnel noise: Caused by the random behavior of charge carriers as they pass through a resistor. For example, in the drain channel of a field-effect transistor, the statistical properties of carriers can lead to the generation of noise voltages.

3. Radio frequency interference: interference caused by external radio frequency signals to circuits or systems. This interference can introduce noise voltage through conduction, radiation, intermodulation, etc.

4. Power supply noise: caused by instability and stray components in the power supply. Ripples, ripples and other power disturbances in the power supply can cause noise voltages to be generated.

Measuring noise voltage is a critical step in understanding and evaluating system performance. Commonly used measurement methods include root mean square value measurement, spectrum analysis, autocorrelation function measurement, and random process analysis. These methods can help engineers better understand the characteristics of noise voltages and thereby optimize the design and performance of electronic systems.