The performance of power amplifiers is fundamentally governed by the conduction angle (θ), which establishes the trade-off between collector efficiency, power dissipation, linearity, and harmonic distortion. This paper presents a comparative analytical study of the operating characteristics of the four principal power amplifier classes: Class A (θ = 360∘), Class B (θ = 180∘), Class AB (180∘<θ<360∘), and Class C (θ<180∘), evaluated under different biasing conditions. The relationship between biasing and conduction angle is first established, followed by analytical derivations of collector efficiency, DC power dissipation and the principal performance characteristics of each amplifier class. The analysis demonstrates that the power conversion efficiency is improved by reducing the conduction angle, which lowers average DC current and internal power dissipation. This improvement comes at the cost of increased harmonic distortion and reduced linearity. Conversely, increasing the conduction angle enhances signal fidelity and linear operation at the expense of efficiency and thermal performance. The study confirms that Class A amplifiers provide the highest linearity but the lowest efficiency, Class B improves efficiency while introducing crossover distortion, Class AB offers the most practical compromise between efficiency and signal fidelity, whereas Class C achieves the highest efficiency for tuned radio-frequency applications. The presented analysis provides a systematic basis for selecting an appropriate power amplifier topology according to the efficiency, linearity, distortion and thermal requirements of audio and RF systems.......................... Keywords: .........................Power amplifier, conduction angle, class A amplifier, class B amplifier, class AB amplifier, class C amplifier, efficiency, linearity, harmonic distortion, power dissipation.