Elec 160 Module 8 Laboratory - Page 1 ELEC 160 Electronics I

Elec 160 Module 8 Laboratory - Page 1 ELEC 160 Electronics I Module 8: AC amplifiers based on JFETs

Build and analyze a common source amplifier circuit, measure its voltage gain, input impedance, and output impedance using experimental techniques and calculations, including taking measurements with an oscilloscope and applying relevant formulas. Document your measurements, calculations, and observations comprehensively in a lab report, including circuit diagrams and waveforms. Reflect on difficulties encountered, insights gained, and relevance to coursework.

Paper For Above instruction

The objective of this laboratory experiment is to explore the characteristics and measurement techniques of JFET-based AC amplifiers, focusing on the common source configuration. Understanding these parameters is essential for designing and analyzing low-noise, high-gain amplifier stages in analog electronics. The experiment emphasizes practical measurement methods, including voltage gain, input impedance, and output impedance assessments, which are integral to effective circuit analysis and design in both academic and professional contexts.

The procedure initiates with constructing a common source amplifier circuit as illustrated in the provided schematic. Upon assembly, an oscilloscope is used to measure the voltage gain (Av = Vout/Vin) of the amplifier, which determines the amplification factor of the circuit. Accurate measurement of gain involves observing the input and output waveforms, ensuring sensible input signal levels to avoid distortion. This step underscores the importance of signal integrity and proper measurement techniques in experimental electronics.

The subsequent task involves measuring the input impedance of the amplifier. This technique employs inserting a known resistor (R4) in series with the input, then measuring voltage drops across the resistor to calculate input impedance based on voltage division principles. This method is practical for live circuits, providing insights into how the amplifier interacts with source impedances and affects overall system performance. It reinforces key concepts in impedance matching, crucial for maximizing power transfer and minimizing signal reflection.

To measure the output impedance, a practical approach involves applying a load resistor at the amplifier’s output and measuring the output voltage with and without the load. Using the load voltage (Vload) and the open-circuit output voltage (Vout), the output impedance can be calculated. Proper selection of the load resistor is essential, often requiring iterative adjustments to obtain accurate representation of the amplifier's output impedance in real-world scenarios. This measurement is vital in understanding how the circuit will behave when connected to various loads in actual applications.

In the comprehensive lab report, students are expected to document their experimental setup with circuit diagrams, record all measured values, perform relevant calculations using provided formulas, and include screenshots of waveforms obtained from the oscilloscope. The report should also contain a detailed analysis of the results, discussing how measured values compare with theoretical expectations, any deviations observed, and potential sources of error. These reflections are crucial for developing practical skills and understanding the nuances of electronic measurement techniques.

The final part involves a written conclusion addressing difficulties faced during the experiments, insights gained regarding AC amplifier operation and impedance measurement, and the relevance of these findings to coursework and real-world applications. Such reflection encourages critical thinking and consolidation of theoretical knowledge through hands-on practice, reinforcing the importance of accurate measurement and analysis in electronic circuit design and troubleshooting.

References

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