50 Watt audio power amplifier circuit

50 Watt audio power amplifier circuit

50 Watt audio power amplifier circuit

The LM1875 is a monolithic power amplifier offering very low distortion and high quality performance for consumer audio applications. The LM1875 delivers 20 watts into a 4Ω or 8Ω load on ±25V supplies. Using an 8Ω load and ±30V supplies, over 30 watts of power may be delivered.
The amplifier is designed to operate with a minimum of external components. Device overload protection consists of both internal current limit and thermal shutdown.

50 Watt audio power amplifier parts

50 Watt audio power amplifier circuit parts

The LM1875 design takes advantage of advanced circuit techniques and processing to achieve extremely low distortion levels even at high output power levels. Other outstanding features include high gain, fast slew rate and a wide power bandwidth, large output voltage swing, high current capability, and a very wide supply range. The amplifier is internally compensated and stable for gains of 10 or greater. This circuit diagram 50Watt Hi-Fi Power Amplifier based on LM1875 ICs and BD249 – BD250 bridge transistors. It has good input sensitivity, low distortion, good operating stability and full protection against overloads and output short-circuits. It can be used as a booster amplifier for existing small systems or to drive a second pair of speakers besides the ones already connected to the system. The board needs a symmetrical power supply of ±18V – 25V dc/4A and can be connected to 8 or 4 Ohm speakers. Large heat sink is required for this circuit. Diagram shown below indicates only the left channel. Make two circuits for stereo version.

50 Watt audio power amplifier pcb

50 Watt audio power amplifier circuit pcb

The output coil L1 using l mm enameled wire wound resistor in R9 3W without being tightly wound 10 turns on. Power section using dual-18V 150W high-quality toroidal transformer, 35V/4700μF the filter capacitor 4, 35V/100μF two, 100V/0.1μF two, insurance management FUSE1, FUSE2 use 4A.

Technical Specifications:

Supply voltage = ±25Vdc/4A symmetrical (see text)
Current consumption = 3A maximum
Input impedance = 47K Ohms
Input sensitivity = 650 MV
Signal to noise ratio = 90 dB
Frequency response = 20 - 20,000 Hz ± 1 dB
Distortion = 0.5 % maximum
Load impedance = 4 - 8 ohm

R1 = 47k–1/2w
R2 = 1,2K–1/2w
R3 = 47k–1/2w
R4 = 1R – 2,2R – 4w
R5 = 1R – 2,2R – 4w
R6 = 0.22R – 4w
R7 = 0.22R – 4w
R8 = 22R – 3w
R9 = 10R – 3w

C1 = 4,7uf-25V
C2 = 100uF-25V
C3 = 1000uF-33V
C4 = 1000uF-33V
C5 = 100nF-62V
C6 = 100nF-62V

L1 = (see text)

Q1 = BD249
Q2 = BD250

IC = LM1875


PCB Parts
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