Lm4782 Circuit audio power amplifier circuit 3X 25W


Circuit audio power amplifier using integrated lm4782 overture for three channels of 25W with mute and stand-by

LM4782 is audio amplifier of three channels capable to supply 25W of potency for channel.

LM4782 uses the system of protection of National Self Peak Instantaneous Temperature (˚Ke) (SPiKeTM). Spike protects the exit of the lm4782 of on tension on load, short of the source for gnd, temperature protection and picks instantaneous of temperature. Each amplifier of the lm4782 has a mute circuit and internal stand-by, that can be controlled by logic it expresses. LM4782 can be configured to be used in bridge or in parallel way without complications, it exists several ways to use integrated him. To know more on spike it seeks for AN-898 in the site national.com .

Description of the operation of the circuit of the amplifier with lm4782

The circuit described here it is treated of the application suggested by the national semiconductors for an amplifier of potency of three channels with having integrated lm4782. To determine the heat-sink to be used it sees the datasheet of the lm4782.

In the way stand-by the drain of current of the source VCC is less than 30µA for all amplifiers and chain drained of the source VEE is typically of 8mA.

Bypassing Capacitors

To eliminate possible oscillations or instability in low frequency high frequency either is used a capacitor electrolytic or of tantalum to absorb variations in low frequency and a ceramic capacitor to prevent feedback in discharges frequencies. those components are placed in the power lines.

Filter high raisin

The combination of it Laughs with ci it creates a filter high raisin. The frequency answer is determined by those two components. The point of -3dB can be found using the equation below:

fi=1/(2ÀRiCi) (Hz)

If a capacitor of blockade dc be used, there is another filter it passes discharge servant with the combination of Cin and Rin. When great values of Rin are used it can happen oscillations in the exit.

To determine the type of the heat-sink and other assembly configurations it sees the datasheet of the lm4782.

Source for the circuit

That proposed circuit requests a symmetrical source of +-25volts that is capable. Just use a good transformer, rectificators and great capacitors of filter of at least 10000µF. The transformer uses transformer toroidal preferably.

Schematic of the circuit of the potent amplifier with lm4782

Lm4782 Circuit Audio Power Amplifier Circuit 3X 25W

Printed circuit board (couple face) side of the it welds suggested by the national for assembly of the potent amplifier of three channels

Pcb Lm4782 Circuit Audio Power Amplifier Circuit 3X 25W

Circuit board (couple face) printed side of the components suggested by the national for assembly of the amplifier

Pcb Lm4782 Circuit Audio Power Amplifier Circuit 3X 25W

Assembly of the components of the amplifier in the board

Pcb Lm4782 Circuit Audio Power Amplifier Circuit 3X 25W

silkscreen of the board of the amplifier

It lists of material for assembly of the amplifier

Name value tolerance type /description
RIN1,RIN2,RIN3 33k 5% 1/4 watt
RB1,RB2,RB3 1k 1% 1/4 watt
RF1,RF2,RF3 20k 1% 1/4 watt
Ri1,Ri2,Ri3 1k 1% 1/4 watt
RSN1,RSN2,RSN3 4.7 5% 2 watt
ID 2.7 5% 1/4 watt
RV 5.1k 5% 1/4 watt
CIN1,CIN2,CIN3 1µF 10% Film metallic polyester
CN1,CN2,CN3 15pF 20% Ceramic
Ci1,Ci2,Ci3 68µF 20% Ceramic Radial / 35V
CSN1,CSN2,CSN3 0.1µF 20% Ceramic
CV 0.1µF 20% Ceramic
CS1,CS2 0.1µF 20% Ceramic
CS3,CS4 10µF 20% Radial Ceramic /50V
CS5,CS6 2,200µF 20% Ceramic Radial / 50V
S1,S2 Key SPDT (on-on)
J1,J2,J3 PCB Montage RCA
Jack J5,J7,J9,J11 PCB Banana Jack – Black
J4,J6,J8,J10,J12 PCB Banana Jack – Red
VZD 5.1V Zener Diode 1W
U1 LM4782 TO-220

For more information to do download of the datasheet of the lm4782

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About the author
Xtronic.org blog author. Electronics technician for the technical school of Brasilia - Brazil. Interested in electronics, circuits and technology in general.

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