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Class A Amplifier Design

  1. Nov 25, 2011 #1
    1. The problem statement, all variables and given/known data
    EE3350 Electronics I Term Project
    "Power Amplifier Design"
    Objective:
    You will be designing a proper power amplifier for Good Speakers, Inc. The company will accept only two designs. One of
    them is Class A amplifier and the other one will be a Class B amplifier. Your design should satisfy the minimum design
    requirements that are given in Section A. After carefully reading the design requirements, you need to follow the process and
    deadline sections carefully in order to get full credit. If you miss the deadline you will get zero for that section of the project and
    that can impact on your overall grade. You need to present your work to company executives. You must use a PowerPoint
    presentation and each group member should be familiar with the project. The company executives will ask questions to
    individual group members. The answers provided by group members can impact your overall grade. After completion of the
    presentations, the winning groups will be announced during our "After the Presentations" Party. Donuts and soft drinks will be
    supplied by Good Speakers, Inc. We thank them for their generosity.
    Section A - Design Requirements:
    Your amplifier should have the following specifications.
    • Input comes from a voltage source with 50 Ohms source resistance. The collected data shows that input voltage is
    sinusoidal and ranges between 0 volts to 2 mV peak-peak values.
    • Output is a speaker with resistance values that change between 2 Ohms to 16 Ohms.
    • Onboard 12 V DC power supply (You may consider -12 Volt DC Power supply if desired).
    • USB connector for charging purposes (Even though this is not part of the original project, the company wants to
    know if this is possible. You need to show the details and cost analysis during your presentation).
    • High power gain
    • High efficiency required
    • Minimum cost per design
    • 1 layer PCD
    • Minimum PCB area
    You may suggest changing any of these design requirements to the company with written alternative design specifications
    that explain why your suggestions can improve the design.
    These design requirements are subject to change by the company at any given time. You will be notified by the company
    via e-mail. Please check your e-mail regularly.
    2. Relevant equations
    DC values
    Vb=(R2/(R1+2))Vs
    Ve=Vb -0.7V
    Ie=Ve/Re
    Av=Vout/Vin
    Ie=Ic
    Vc=Vcc-IcRc
    Vce=Vc-Ve



    3. The attempt at a solution

    I only have thought of some general ideas based on what little I know. One of my ideas was just a simple CE Amplifier VDB with a cascading CE and CC and maybe use a zener diode for voltage regulation at the base. I haven't had time to work out the values for my compenents either just kind of fleshed it out in multisim real quick and wanted to get an idea of what some of you guys would do.
     

    Attached Files:

  2. jcsd
  3. Nov 25, 2011 #2
    In a class A amplifier the output voltage needs to swing equally + and- .
    This means that V at the collector of the transistor... with no input should be Vsupply/2
    With Rc = 2.2k and Vs = 15V this means a collector current of 3.4mA
    The potential divider R1 and R2 should provide a voltage at the base which will produce an emitter current of about 3.4mA (Ic≈Ie)
    Check your calculations, I get the same values as you. You seem to have the class A amplifier sorted out
    sorry... I did not include that there is a Vce across the transistor....it is not much but may make a slight difference to your numbers.
    Hope you can cope with it
     
    Last edited: Nov 25, 2011
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