12V 50 watt audio amplifier

LM3876 is a high performance audio power amplifier IC from National Semiconductors. The LM3876 can deliver 50watts of output power into an 8 ohm loudspeaker. LM3876 has excellent signal to noise ratio and has wide supply voltage range. Other features of LM3876 are output to ground short circuit protection, input mute function, and output over voltage protection, etc. Applications of LM3876 are component stereo, compact stereo, surround systems, self powered speakers, etc.


The 50 watt audio amplifier  circuit shown below is designed based on the application diagram from the data sheet of LM3876. Some modifications are made on the original circuit for improving the performance. The bipolar electrolytic capacitor C7 is the input DC decoupling capacitor. R4 is the input resistance. R2 & R1 and bipolar electrolytic capacitor C5 forms a feedback circuit. C2, C1 are filter/by-pass capacitors for the positive supply rail. C4 & C3 are the filters/by-pass capacitors for the negative supply rail. The feedback resistor R2 sets the gain of the amplifier. L1 provides high impedance at high frequencies so that R7 may decouple capacitive loads. R3 is the mute resistance which allows 0.5mA to be drawn from pin8 to turn the mute function OFF. S1 is the mute switch. Resistor R6 and capacitor C8 forms a Zobel network which improves the high frequency stability of the amplifier and prevents oscillations.

Circuit diagram

12v 50w audio amplifier


  • The LM3876 can be operated from a supply voltage range of +/-12V to +/-49V DC.
  • I recommend +/-35V DC for powering the IC.
  • LM3876 requires a proper heat sink.
  • Quiescent current of LM3876 is around 70mA




  1. Sir, can i power this circuit using 12 0 -12…….. i am searching for a car amplifier for a 40 W speaker, is this one is suitable.

  2. Midhundas

    Sir how much power can i expect frm this circuit when i Use a 24 0 24 Power supply?

  3. Can anybody tell me the recommended wattage of R7…plz help me

  4. I have a dual power supply of 35-0-35 v. But, the ampere rating of that power supply is 3 Amperes. Will this circuit work on that power supply?? Or the current provided will be high enough to burn the circuit??

  5. seetharaman

    sir can i ask a substitute transistor for D1047S

    • Seetharaman

      140V/12A AF 60W NPN Triple Diffused Planar Silicon Transistors with an hfe of 100 to 200 and ft of 15MHz. the recommended equivalents are 2SC3284 2SC4466

    • seetharaman

      Hi led950 this circuit is a proven amplifier design. you can take for granted and proceed with the construction, taking standard care in the layout etc.

    • Seetharaman

      Hi lcd950 please go through the notes given below the circuit it can work on any voltage from +/-12V to +/-49V DC, both – & + potential should be identical in value.

  6. Hello sir,
    i want the complete power supply circuit design for this circuit with +35V & -35V for its best working. Please give mi this circuit by mail or if possible publish here.

  7. It’s amazing to have this at time, hope to use in my project…………….

  8. Arnel Millet

    Nope! How come it’s different circuit? It’s a MOSFET amp, instead of LM3876.,,,,

  9. jay james

    No IC LM3876 amplifier here.

    Just a 50 watt mosfet amplifier instead.