60w power audio amplifier

60W Power Audio Amplifier Circuit with 2N3055

This is a simple 60W class B power amplifier. This audio amplifier can work from 30 to 60V with the maximum input voltage around 0.8 – 1V. It is built with the well known 2N3055 and can deliver up to 80W on a 4Ω speaker.

60W audio power amp circuit schematic

60w power audio amplifier


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  • billbo_dbigpond-com

    I would like to post the schematic here but I cannot find a way to upload the cicuit with the new resistor values and transistors I used.
    Can someone help?
    Billy D…

  • msdava

    simetrik bir anfi deyil fakat simetriğe çevirmek basit bu amp

  • Billbo

    Hi. I have built this cct. on vero board and works a treat! I have used slightly different resisyor values to suit a 75 volt single supply and the output is about 55 watts REMS into 8 ohms and about 65 watts RMS into 4 ohms. Very simple build and good distortion figures were measured. 0.06% at 50 watts rms 8 ohm load at 69 volts.
    Billy D…

    • tunmaker

      Hi i know its a long time since you posted this but can you provide the circuit and resistors values that you tweaked for you circuit it would be much appreciated as i am trying to build one my self


  • archie

    can someone pls explain the working of this circuit?
    i need it ASAP…thanks

    • Billbo

      Jim Keith you explained it very well. Congrats to you sir…
      Billy D…

    • Eddy

      Hi sir how are U I send my Email I have a diagram 2n3055 amp all transistor but this one has 2 RV one bias and the other one just to make center 0 volts here is my Email if u want me to send to u and take look what do u think about I have amp stereo 50 Watts it work perfect the 2N3055 they work cool u know what it mean thanks for u help;;;;;;;;;

    • Jim Keith

      The PNP input stage is configured as a common emitter amplifier with lots of current feedback through the emitter resistor that is tied to the output bus. It also regulates the DC operating point of the output bus. With feedback as such, it has essentially unity AC and DC gain. The top left capacitor and resistor are noise decoupling for the bias source for the input transistor to keep it from amplifying the power supply noise and ripple.

      A signal is picked off the collector resistor to drive the base of the lower BD286. It is the high voltage gain element and requires a frequency compensation cap (C2) to prevent oscillation. C1 and the resistor above it also provide frequency comp by reducing the AC feed back to the input stage.

      The BC107 is the bias regulator that develops approx 3 junction drops (1.95V) to properly drive the complementary transistors (top BC286 and the BC287). If the bases of these two transistors were tied together, it would be a zero bias class B, but the bias regulator develops just enough voltage to put the complementary transistors just on the edge of conduction. The complementary transistors are both connected in the common collector configuration (emitter followers) so they have essentially unity voltage gain.

      Coupled to the BC286 is the 2N3055 in a Darlington configuration. The lower 2N3055 is connected to the BC287 in a composite connection that essentially turns the BC287 into a high current gain PNP transistor.

      The 100-200uf capacitor is a “bootstrap” capacitor that couples the output bus to the 1-3K pullup resistor. In this way, the anode of the capacitor actually transcends the bus voltage when the output bus goes positive so that the BC286 has lots of base drive and can easily turn on fully.

      The 1500uf coupling cap keeps the DC portion of the output bus voltage off the speaker. Since the speaker is a reactive load (especially at high audio frequencies), the reactance is reduced via the 100nf, 10Ω resistor –helps prevent oscillation.

  • shitaljit

    No any comments.

  • JuliusC.Horfilla

    how much output power we get, if use 8 2n3055 power transistors in the output stages with a .33 ohms resistor attached on each transistor.instead of only 2 2n3055 power transistors.thanks.

    • shitaljit

      First you must deside how much output you are required, then arrange amplifier circuite accordingly ,2n3055 transistor required is only base on your output,nothing else any limitation.


  • Sagacity61

    Isn’t RV 500 meant to null to zero VDC at the output?

  • Eddy Vila

    hi I build stereo 60W Power Audio Amplifier with 2N3055 it work very good but the RV 500 ohm not working if somebody have any idea what going on here I got power supply with 60 V DC but on the mild connection it will be 30V DC

  • bry

    i just need its pcb layouts and parts list! thank you and good day!

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