250mW audio amplifier

john April 7, 2010 11 Comments

Description.
Here is a very simple three transistor audio amplifier circuit that can deliver 250mW to a 8Ohm speaker. Complementary transistors BC337 and BC227 (Q3 and Q2) are used as the output pair. Transistor Q1 (BC 547) acts as the preamplifier.POT R5 can be used as a volume control. Capacitor C1 decouples the DC from the audio source. Resistor R2 ensures better stability for the amplifier.This amplifier is very suitable for application in small radio sets and as a preamplifier in high power audio amplifiers.

Circuit diagram.

250mw-audio-amplifier-circuit

Notes.

  • The circuit can be powered from 9V DC.
  • Assemble the circuit on a Vero board.
  • K1 can be an 8 Ohm speaker.
  • For better performance, properly decouple the input and output grounds.
  • POT R5 can be used for adjusting volume.
Comments
  • nitesh
    May 17, 2015

    hay… i m confused.. that input 9v… where were the -ve terminal…. ple help me…

  • shrawan
    November 1, 2014

    I have pcb layout of this circuit diagram..pls send to my mail id

  • Sh Ehsan
    May 30, 2014

    Can you tell me how did you find these values of resistors and capacitors.?

  • Afzz
    April 26, 2014

    This is very good,very simple circuit i’ve ever seen..,good job…i’ll try to make it.but my question is,can I replace other transistor to change bc337(NPN) ,bc 327(PNP)..or bc547..?i don’t have such transistor right now.

    • Seetharaman
      April 27, 2014

      You can use any NPN PNP with a rating of vceo 25 volt ic 800ma and ptot 1 watt. 8050(NPN) 8550(PNP) 2N1711, 2N2905 SK100 / SL100 etc etc.

  • Jonathan
    July 13, 2011

    Laeeq; You can find a nice amplifier IC schematic at http://www.datasheetcatalog.org/datasheet/philips/TDA7052_CNV_2.pdf . Copy this address and paste into the address box and then look at page 6 in the pdf for the schematic. The chip is cheap and many suppliers have it. Mouser has it for $1.14 US. Order TDA7052AN. If you can’t find this chip you can always find plenty of info on the LM386, which is the industry standard for low-voltage/power amps.

  • Laeeq
    January 24, 2011

    i want to use 3v bettery in this circuit. can i do? how?

  • February 16, 2010

    Do I wrong or Q2 should be a BC327?

    • admin
      February 16, 2010

      Q2 is BC327.
      I have corrected the circuit diagram.

  • shivek
    August 27, 2009

    hey you r doing a great job for the carrier of many engineers. and i greatfully thanks to you.

  • mozifur
    August 20, 2009

    I am benifited to receive these circuits.

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