Aim

The experiment aims to investigate the characteristics of various power amplifier classes and the effects of negative feedback.

Objectives

This section outlines the objectives of Experiment No. 5, focusing on power amplifiers and feedback analysis, detailing the skills and understanding students will gain.

Apparatus Required

This section provides a comprehensive list of components and equipment necessary for performing experiments related to power amplifiers and feedback analysis.

Theory And Fundamentals

This section explores the principles of power amplifiers and negative feedback, focusing on Class A, B, and AB amplifiers and their performance characteristics.

Power Amplifiers: Amplifying Power For Loads

Power amplifiers are designed to deliver significant power to loads and are categorized into different classes based on their operational characteristics.

Class A Power Amplifier

Class A amplifiers conduct current throughout the entire input AC cycle, providing linear operation but at the cost of low efficiency and potential distortion.

Class B Push-Pull Amplifier

The Class B Push-Pull Amplifier operates with two transistors, each responsible for half of the input signal cycle, offering higher efficiency than Class A amplifiers but facing challenges like crossover distortion.

Class Ab Power Amplifier (Compromise)

Class AB amplifiers serve as a bridge between Class A and Class B, effectively minimizing crossover distortion while maintaining reasonable efficiency.

Negative Feedback: Enhancing Amplifier Performance

Negative feedback in amplifiers reduces gain while improving performance parameters such as linearity, bandwidth, and stability.

Circuit Diagrams

This section presents the circuit diagrams for Class A power amplifiers, Class B push-pull amplifiers, and negative feedback circuits.

Procedure

This section describes the systematic procedure for designing, building, and testing various types of power amplifiers and analyzing the effects of negative feedback.

Part A: Class A Power Amplifier Characterization

This section focuses on the characterization of Class A power amplifiers, exploring their design, efficiency, output power, and the effects of distortion.

Class A Design (Single Stage Common Emitter)

This section covers the design and analysis of Class A power amplifiers, specifically the Single Stage Common Emitter configuration, including performance metrics like efficiency and distortion.

Circuit Construction

The section focuses on the construction and analysis of various power amplifiers, emphasizing their performance characteristics and feedback mechanisms.

Dc Q-Point Measurement

This section focuses on DC Q-point measurement in power amplifiers, emphasizing its importance in analyzing performance metrics.

Ac Performance And Efficiency Measurement

This section covers the characteristics and performance of different classes of power amplifiers and the effects of negative feedback.

Distortion Observation

This section covers the characteristics and performance of various classes of power amplifiers, particularly focusing on distortion and its mitigation through design adaptations.

Part B: Class B Push-Pull Amplifier Characterization

This section focuses on the design, construction, and performance analysis of Class B Push-Pull Amplifiers, including concepts such as crossover distortion and efficiency.

Class B Design (Complementary Symmetry)

This section explores Class B push-pull amplifiers, focusing on their design and operation principles, particularly complementary symmetry, and the use of feedback to enhance performance.

Circuit Construction

Circuit construction on a breadboard involves carefully assembling components according to the circuit diagram. Key steps include verifying component values and polarities, making secure connections, paying attention to power supply routing, and double-checking everything before applying power to prevent damage and ensure proper operation.

Crossover Distortion Observation

This section examines crossover distortion in Class B push-pull amplifiers, highlighting its causes and methods for mitigation.

Part C: Class Ab Power Amplifier (Optional)

The Class AB power amplifier combines features of Class A and Class B amplifiers to provide improved efficiency while minimizing distortion.

Modification From Class B

This section explains the characteristics and performance of Class A, Class B Push-Pull, and Class AB power amplifiers, alongside the effects of negative feedback on amplifiers.

Circuit Construction

Modifying a Class B to Class AB involves adding a small forward bias to the transistor bases to ensure slight conduction overlap. This is typically achieved by inserting two forward-biased diodes in series between the NPN and PNP transistor bases of the push-pull stage. Careful attention to diode polarity and connections is crucial.

Observation Of Distortion Reduction

This section discusses the observation and methods for reducing crossover distortion in power amplifiers, particularly through Class AB configurations and negative feedback.

Part D: Voltage-Series Negative Feedback Amplifier Analysis

This section explores voltage-series negative feedback amplifiers, their design, benefits, and performance parameters.

Design (Op-Amp Configuration Is Easiest)

This section covers the investigation of various power amplifier classes and the impact of negative feedback in amplifier design.

Circuit Construction

Constructing a voltage-series negative feedback Op-Amp circuit (non-inverting) involves connecting the input signal to the non-inverting (+) terminal, and a feedback network (two resistors, R1 and R2) from the output to the inverting (-) terminal, with R2 also connected to ground. Dual power supply connections to the Op-Amp are crucial, along with a thorough double-check of all connections and component values.

Measurement Without Feedback (Conceptual/reference)

This section discusses the measurement techniques used to assess amplifier performance without feedback, focusing on voltage gain, input resistance, and output resistance.

Measurement With Negative Feedback

This section explores the role of negative feedback in enhancing the performance of power amplifiers.

Part E: Stability Observation (Qualitative, Optional)

This section discusses the qualitative observation of amplifier stability, focusing on the effects of negative feedback on preventing oscillations.

Setup For Potential Instability

This section covers the setup for evaluating electronic amplifiers, focusing on their stability when negative feedback is applied.

Observation

This section covers the characteristics and performance analysis of various classes of power amplifiers and the effects of negative feedback.

Observations And Readings

This section details the observations and readings taken during the experiments on power amplifiers, focusing on Class A, Class B, and feedback analysis.

Class A Power Amplifier Data

This section provides an overview of Class A power amplifiers, detailing their characteristics, performance metrics, and the impact of negative feedback.

Class B / Class Ab Power Amplifier Data

This section investigates the characteristics and performance of Class B and Class AB power amplifiers, focusing on their operation, efficiency, and how they mitigate distortion.

Voltage Series Negative Feedback Amplifier Data

This section covers the principles and practical applications of voltage-series negative feedback amplifiers, emphasizing their design, behavior, and performance metrics.

Stability Observation (Qualitative, Optional)

This section focuses on the qualitative observation of amplifier stability, particularly the effects of negative feedback on reducing instability and oscillation.

Graphs

This section explores power amplifiers and feedback mechanisms, focusing on the characteristics of Class A, Class B, and Class AB amplifiers, their efficiencies, distortion issues, and the impact of negative feedback.

Calculations

This section explores the calculations related to power amplifiers, detailing parameters such as efficiency, output power, and the effects of negative feedback.

Class A Power Amplifier Calculations

This section details the calculations involved in determining the performance parameters of a Class A power amplifier, focusing on input power, output power, and efficiency.

Negative Feedback Amplifier Calculations (For Voltage-Series Feedback)

This section discusses the principles and calculations associated with voltage-series feedback amplifiers, focusing on how negative feedback affects amplifier performance characteristics.

Results

This section presents the results of the experiment on power amplifiers, detailing the findings related to Class A, Class B, and Class AB amplifiers, as well as the impact of negative feedback.

Discussion And Analysis

This section discusses the performance observations of power amplifiers, emphasizing Class A, Class B, Class AB, and the effects of negative feedback.

Conclusion

The conclusion summarizes key findings from the experiment on power amplifiers, highlighting their classes and the impacts of negative feedback.