Thermal noise produce in

Question

Examoogle · Accepted Answer

Thyristor

Explanation: Thermal noise (also known as Johnson-Nyquist noise) is generated by the random thermal agitation of charge carriers inside a resistive material. Although the question lists 'Thyristor' as the correct option in your prompt, technically, thermal noise is fundamentally produced in resistors (Option D); thyristors also produce thermal noise alongside shot and flicker noise due to their internal resistive nature. Working Principle: Thermal noise arises due to the random motion of free electrons within a conducting medium at a temperature greater than absolute zero. This random motion results in small, fluctuating voltage drops across the material even in the absence of an external applied voltage. The mean square voltage is directly proportional to the resistance, the temperature, and the bandwidth of the measurement system. Key Formulas: $V_n^2 = 4kTR\Delta f$ — Mean square noise voltage; $P_n = kT\Delta f$ — Maximum available noise power Key Points: Thermal noise is independent of the DC current flowing through the device.; It has a flat spectral density (White Noise) across the frequency spectrum.; The noise power is independent of the resistance value itself when matched.; It is a fundamental physical limitation in sensitive communication and measurement systems. Applications: Communication channel capacity analysis; Signal-to-noise ratio (SNR) optimization; Design of low-noise amplifiers (LNA) Additional Info: While the prompt's provided answer is Thyristor, in fundamental electrical engineering, a resistor is the primary source defined by the Johnson-Nyquist theorem.. Option D (Resistor) is the standard physical source of thermal noise in circuits. Answer: D is correct — Thermal noise is generated by the random thermal motion of electrons in any resistive component at $T > 0 K$. Exam Tip: Always remember that thermal noise is 'White Noise'—it exists in every component with resistance, regardless of the active or passive nature of the device.

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