Comparative Analysis of Miller Effect in RC-Coupled, Transformer-Coupled, and Direct-Coupled Amplifier Stages
Keywords:
Bipolar junction transistor (BJT), Frequency response, LTspice simulation, Miller effect, Voltage amplifierAbstract
This study presents a comprehensive experimental and simulation-based comparative analysis of the Miller effect in three widely used amplifier configurations, RC-coupled, transformer-coupled, and direct-coupled BJT amplifier stages. The Miller effect significantly influences high-frequency performance by increasing the effective input capacitance through internal feedback. In this work, both hardware experimentation and LTspice simulations were performed under identical biasing and operating conditions to ensure consistency. Key parameters such as voltage gain, effective input capacitance, and upper cutoff frequency were evaluated. The results show strong agreement between experimental and simulation data. The direct-coupled amplifier exhibits the highest Miller multiplication and lowest bandwidth, while the transformer-coupled amplifier demonstrates superior high-frequency performance due to reduced effective capacitance. The RC-coupled amplifier provides a balanced trade-off. This study provides practical insights for selecting appropriate coupling techniques in high-frequency analogue circuit design.
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