Hi-Fi 120W RMS Amplifier using LM4780 IC + PCB

Fig. 1 – HI-FI 120W RMS Amplifier Circuit using LM4780 IC

This is a HI-FI Audio Amplifier circuit with high quality with a large frequency response, using Integrated Circuit LM4780 which is a stereo audio amplifier.

Capable of providing normally 60W per channel of average power of continuous output on an 8Ω load with less than 0.5% THD + N from 20Hz to 20kHz.

LM4780 General Description

The LM4780 is fully protected utilizing National’s Self Peak Instantaneous Temperature (˚Ke) (SPiKeTM) protection circuitry.

SPiKe provides a dynamically optimized Safe Operating Area (SOA). SPiKe protection completely safeguards LM4780‘s outputs against over-voltage, under-voltage, overloads, shorts to supplies or GND, thermal runaway and instantaneous temperature peaks.

The advanced protection features of LM4780 places it in a class above discrete and hybrid amplifiers.

Each amplifier of LM4780 has an independent smooth transition fade-in/out mute. The LM4780 can easily be configured for bridge or parallel operation for 120W mono solutions.

Key Specifications

Output Power/Channel with 0.5% THD+N, 1kHz into 8Ω 60W (typ)
THD+N at 2 x 30W into 8Ω (20Hz – 20kHz) 0.03% (typ)
THD+N at 2 x 30W into 6Ω (20Hz – 20kHz) 0.05% (typ)
THD+N at 2 x 30W into 4Ω (20Hz – 20kHz) 0.07% (typ)
Mute Attenuation 110dB (typ)
PSRR 85dB (min)
Slew Rate 19V/µs (typ)

The Circuit

In Figure 2 below, we have arrangement of amplifier circuit components with LM4780 IC, and as we can see, there are few external components.

It is making the amplifier circuit very simple to assemble, one must be careful when assembling the circuit, so as not to invert any component, as it may suffer circuit burnout.

Fig. 2 – Schematic diagram of Hi-Fi Amplifier 120W RMS with IC LM4780

Features

SPiKe protection
Few external components
Silent fade-in / mute out mode
Wide range of supply voltage: 20V – 84V
Signal-to-noise ratio ≥ 97dB (ref. for PO = 1W)

Power Supply

The power supply is a +-35V symmetric power supply. If you want to use it in stereo mode with two channels, it will be necessary to use twice the current to support the power of 240W, 120W per channel.

The power supply must have a good filter to avoid roaring, interference, and oscillations in the amplifier output.

The consumption current for a channel “One integrated circuit“, must be 4 amps, if using two circuits, in stereo mode, the current must be doubled, in this case 8 amps.

The LM4780 must be equipped with a heatsink, if you use the IC without a heatsink, it will burn out.

It is recommended to tinker with voltage and output tracks, since the IC has a tight pinout, making it impossible to widen tracks on the PCB.

Component List

Semiconductors

U1 …………………… Integrated Circuit LM4780

Capacitors

C1 …………………… 1uF Polyester / Ceramic Capacitor
C2 …………………… 4.7uF – 50V Electrolytic Capacitor
C3, C5, C8, C9 … 0.1uF Polyester / Ceramic Capacitor
C4 …………………… 4.7uF Polyester / Ceramic Capacitor
C6, C7 …………….. 47uF – 50V Electrolytic Capacitor

Resistors:

R1, R6, R7 ………. 47k ohm resistor – (yellow, violet, orange, gold)
R2 ………………….. 10k ohm resistor – (brown, black, orange, gold)
R3, R5 ……………. 4.7k ohm resistor – (yellow, violet, red, gold)
R4 ………………….. 3.3k ohm resistor – (orange, orange, red, gold)
R8, R9 ……………. 2.7 ohm resistor – (red, violet, red, gold)

Others

SW1 ………………. Switch on/off – to mute “optional“
P1, P2 …………….. Screw Terminal Type 5mm 2-Pin Connector
P3 ………………….. Screw Terminal Type 5mm 3-Pin Connector
PCB, Wires, Solders, Speaker and Etc.

In Figure 4, we provide the PCB – Printed Circuit Board, in GERBER, PDF and PNG files. These files are available for free download, on the MEGA server, in a direct link, without any bypass.

All to make it easier for you to do a more optimized assembly, either at home, or with a company that prints the board. You can download the files in the Download option below.

Fig. 3 – PCB HI-FI 120W RMS Amplifier Circuit using LM4780 IC

Files to Download, Direct Link:

Click on the link beside: GERBER, PDF and PNG files

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