WEEK 2

Comparison Study of audio amplifier performances using Class AB, B and D topologies in portable audio devices.

In this week, I have to search and take the right circuit diagram for Class D and Class AB amplifier. other than that, I'm doing some discussion with my supervisor about circuit diagram and components that I will use and few things need to be considered before buying all the components.

This is some example of circuit diagram that I had found:

Figure 2: TDA8920BTH 200W Class D Amplifier

Figure 3: UM10155 Discrete Class D High Power Audio Amplifier

Figure 4: Class AB BJT 100W hi-end-audio

Last Thursday, 26 January 2012 at 3pm, there was a meeting with all FYP students at Gemilang Hall. The agenda is FYP updates and System Engineering. 

WEEK 1

Comparison Study of audio amplifier performances using Class AB, B and D topologies in portable audio devices.


For the first week semester 1, 2012, I had a discussion with my supervisor on planning in this research for this semester. After discussion, I have come out with the Gantt Chart for this semester from week 1 until week 15. Figure show below is my Gantt Chart semester 2 FYP.

Gantt Chart S1'2012

On Tuesday, 17 January 2012 at 3pm, there was a meeting with all FYP students and Engineering Design students at Gemilang Hall. In meeting, the management of FYP want us to create a blog for our own project to replaced the logbook.

Logo of Blogger

So, all the information about the project including photos, videos and softcopy of full report must be upload in this blog. Other than that, all the FYP students degree sem 2 have to buy a t-shirt to be wear on Engineer Day in week 14.

INTRODUCTION

Comparison Study of audio amplifier performances using Class AB, B and D topologies in portable audio devices.

Amplifier plays an important role in an audio system. As it simply amplify the input audio signal to a certain power level to drive the speaker to bring the original desired signal to live. In recent market, Class AB amplifier seems to be dominating the audio market. Class B operation is opposite of Class A.

Figure 1: Class B, AB and D Amplifier

Class B amplifiers are those in which the output transistors only conduct during half (180 degrees) of the signal waveform. To amplify the entire signal, they use two transistors, one conducting for positive output signals and the other conducting for negative outputs. Class B amplifiers are much more efficient than Class A amplifiers, but they have high distortion due to the crossover point when the two transistors transition from on to off.

Class AB amplifiers combine Class A and Class B to form an amplifier with more efficiency than Class A but with lower distortion than Class B. This performance is achieved by biasing both transistors to conduct near zero signal output-the point where Class B amplifiers introduce nonlinearities. They then transistor to Class B for large excursions.

Class D amplifiers are those that output a switching waveform at a frequency for higher than the highest audio signal that needs to be reproduced. The lowpass-filtered, average value of this waveform corresponds to the actual required audio waveform. This amplifiers are highly efficient (often up to 90% or higher) because the output transistors are either fully turned on or off during operation. Modern Class D amplifiers achieve fidelity comparable to Class AB.

SYNOPSIS

Comparison Study of audio amplifier performances using Class AB, B and D topologies in portable audio devices.

In battery-powered portable audio devices such as mobile phones and MP3 playes, the audio amplifier takes a significant portion of the system's power budget. As a result, audio equipment  designers have been looking for enhancements to the Class AB topolology.

In this project, comparison studies such as power savings achievable through implementing a newer technology such as open looped Class D and Closed looped Class D against Ab and B will be performed. Differences in power consumption between different implementations of topologies should be studied to determine whether they are large enough to affect the overall power budget will also be performed. Besides the power consumption, other factors such as distortions and noise will be taken into account.

The student is expected to perform extension studies on various amplifier topologies, design, build and perform comparison between these topologies. Knowledge in analog electronics is an added advantage.