audio power amplifier (output stage) class AB design?

i have been assigned to design an AB class audio power (for the final project of a basic course in electronics)amplifier using Opamp : 741 , power transistors BD137,138 , a 12 v. supply , load resistance 8 ohm , voltage gain of 40 dB and cut-off frequency 20 Hz. desperately needing help ! where shall i begin?!

7 Answers

Relevance
  • Anonymous
    1 decade ago
    Favorite Answer

    http://www.uoguelph.ca/~antoon/gadgets/741/741.htm...

    This shows a low power amp just using the 741

    The ohmage is way off

    You'd have to give this some thought because the power transisters will be fed by the op amp and drive the 8 Ohm speaker load.

    • Login to reply the answers
  • 1 decade ago

    No quick answer. EE is NOT a self taught discipline (unless you are independently wealthy and/or have all the free time you need).

    I would suggest reading ch. 5 in the book, "Analysis and Design of Analog Integrated Circuits" by Gray, Paul, et al

    ISBN 0-471-32168-0

    My $0.02

    • Login to reply the answers
  • 4 years ago

    40 dB is a gain of 100 They have made it very hard for you ....an 741 opamp needs a plus and minus supply ...if you have to create a pseudo ov (at six volts) it gets tricky pin 7 goes to plus volts pin 4 goes to negative volts pin 2 (-ve) and 3(+ve) should be halfway between plus and minus pin 6 is the output get two 12 volt supplies connect as +12 0V and -12v add a 10k resistor from pin 3 to 0v and a 1uF from the junction of pin 3 and the 10k resistor and use the free end of the 1 uF as the input gain connect a 100k from pin 6 to pin 2 connect a 10k from pin 2 to 0v gain = 1+100k/10k cut off = 1/(2Pi C R) = 1/(6x 1e-6x 10e3) this gives a 3 dB point at 17Hz that's the basic amplifier (with a gain of 100) you have to add the power output stage to pin 6

    • Login to reply the answers
  • 1 decade ago

    Try starting out with application notes for 741 from different manufacturers. This site may help with contacts...good luck.

    • Login to reply the answers
  • How do you think about the answers? You can sign in to vote the answer.
  • ZORCH
    Lv 6
    1 decade ago

    Your first step is to understand the meaning of class AB. As different than A or B or AB2 or C or D. Much will be clearer after that.

    • Login to reply the answers
  • 1 decade ago

    Horowitz & Hill, 2nd edition, page 186, Figure 4.22 is pretty much what you want...of course it doesnt have the cutoff freq but you can add that with a simple op amp RC filter.

    • Login to reply the answers
  • Anonymous
    1 decade ago

    "where shall i begin?"

    By reading the text book.

    • Login to reply the answers
Still have questions? Get your answers by asking now.