Low cost amplifer.

jacky March 8, 2012 5 Comments

Description.

No big deal here! You can make a decent power amplifier using just three transistors. All components used here can be obtained from your electronic junk box. Also you just need a 9V transistor radio battery to power this circuit. The circuit is ideal for a pocket radio or other hand held audio equipments.

The first part of the circuit here is a preamplifier consisting of transistor Q1(2N2222). The collector of the Q3 is coupled to the base of Q2 (2N2905A),which forms a complementary symmetry pair with Q3 (2N3053). The amplified signal is available at the junction of emitter of two transistors. Checkout audio amplifier circuit too.

Circuit diagram with Parts list.

amplifier-circuit.JPG

Notes.

  • For Q1 you can try with any general purpose NPN transistors like BC107, BC148,etc.
  • For Q2 and Q3 you can try any complimentary power transistors. The result may vary slightly.No problem.
  • The can be also powered from a well regulated and filtered 9V DC power supply.
  • Click Here!. To get the power supply circuit for this amplifier.
  • Checkout LA4555 Audio Amplifier here
Comments
  • xDRon
    March 16, 2013

    I am using 8 ohm speaker with how many watts?

  • Jonathan
    April 8, 2011

    The plus goes to the top at “9V DC”, negative at the bottom
    line.

  • cjsmack
    February 15, 2011

    pls where am i gonna connect the positive and negative of the 9v battery . Please help me

  • Jonathan
    January 28, 2011

    470uF input cap? Really? Try 10k for R5 and about 56-68k for R6 and a 10uF for C1. Also, use 1 ohm max for R1/2. Replacing R3 with a bootstrap of 330 ohm, 100 ohm and a 100uF cap would increase output, as well. Bias could be adjusted with a 1K pot across both diodes. Good luck!

    • paru
      April 25, 2014

      wont the circuit work with the above given values already?

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