30W HiFi Audio Amplifier Circuit using LM1875

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Introduction

In this article, we are going to see a “30W HiFi Audio Amplifier Circuit using LM1875”. The LM1875 is a monolithic power amplifier with minimal distortion and great performance. The monolithic power amplifier LM1875 can deliver exceptional audio performance. Even at high output power levels, it utilizes circuit design that approaches achieving low distortion.

Along with these additional qualities, the LM1875 has a high gain, a quick conversion rate, a broad power bandwidth, a big output voltage swing, a big current capacity, and a huge power supply range. To keep the amplifier stable at gains of ten or even more, internal compensation is used.

LM1875 Features

Up to 30 Watts Output Power
AVO Typically 90 dB
Low Distortion: 0.015%, 1 kHz, 20 W
Wide Power Bandwidth: 70 kHz
Protection for AC and DC Short Circuits to ground
Thermal Protection with Parole Circuit
High Current Capability: 4A
Wide Supply Range 16V-60V
Internal Output Protection Diodes
94 dB Ripple Rejection

LM1875 Specifications

Speaker channels (Max): Mono
Power stage supply (Max): 60V
Power stage supply (Min): 16V
Load (Min): 4ohms
Output power: 20W
Iq (Typ): 70mA
Analog supply (Min): 16V
Analog supply (Max): 60V
PSRR (dB): 95
Operating temperature range (C): 0 to 70

Pinout of LM1875

Pin Number	Pin Name	Description
1	Non–Inverting Input	Noninverting end of Amplifier
2	Inverting Input	Inverting the end of the Amplifier
3	Vee	Negative supply voltage
4	Output	Output of amplifier
5	Vss	Positive supply voltage

Hardware Required

S.no	Components	Value	Qty
1	IC	LM1875	1
2	Resistor	1M,1K, 1 Ohm, 22K, 20K	1, 1, 1, 1, 1
3	Capacitor	2.2uF, 0.1uF, 10uF, 100uF, 1000uF, 0.22uF	1, 2, 1, 1, 1, 1
4	Speaker	4-8 ohm	1

Circuit Diagram

Working Explanation

The single voltage supply is used in this project. The IC’s power will be affected by the voltage of the power supply. If we use a 50-volt DC power source, the IC can provide up to 25 watts of power. We use an impedance load ranging from 4 to 8 ohms. However, we employ the maximum signal supply voltage of 60 volts and power output of 30 watts, which load has an impedance of 8 ohms.

This IC type IC has a protective mechanism with a maximum operating temperature range of -65 to 150°C, so it can be used widely, R4-resistors control input impedance, and C1-capacitors provide connection to the amplifier section inside the IC. R1 and C1 control the frequency of the input signal, while R1 and C2 will filter the noise from the power supply to protect the input from noise.

R5 and R6 resistors are wired in feedback mode and serve to regulate the circuit’s gain. R7 and C5, on the other hand, are utilized to bypass or pass through high noise frequencies to the ground to guarantee great sound output quality. There is the C6 coupling signal out to the load.