Amplifier 120W with LM4780

This is a high quality amplifier with LM4780 circuit from Texas Instruments. The whole construction does not hide any intrigue, and therefore it is suitable for beginners in the field of electronics. Datasheet can be viewed here:

Circuit diagram:

lm4780 amplifier circuit

The LM4780 circuit contains two precision amplifiers, each with an honest power of 60W to an 8 ohm speaker. In the catalog they show the parallel connection of these two internal amplifiers and I use it here. This connection is more advantageous than the „bridge“ connection, because the amplifier can work with a lower impedance of up to 4 ohms. This module contains only one channel, so when designing a 2.0 amplifier, you have to build two of these modules. An external power filter must also be connected to the amplifier, as there are only two small electrolytic capacitors on the board! The entire structure is powered by a symmetrical + -35V source. When building two channels and a common source, it is necessary that the transformer has a power of at least 300W. The LM4780 MUST have a heatsink! Especially pay attention to the polarity of the capacitor C9, it may seem reversed, but it is on purpose. The power paths on the PCB must be tinned, because the housing is relatively small and wider paths will not fit there.

Placement plan:

lm4780 printed circuit board

Printed circuit board:

lm4780 PCB amp

Placement plan and PCB are at 1:1 600 dpi (How to print a PCB design can be found in the post How to print PCB design). Real size PCB is 71,8 x 45,0 mm.

Seznam součástek:
R3,R40R1 3W
R12,R132R2 1W
C1,C2100nF ceramic
C3,C447uF/50V ele.
C51uF/50V ele.
C8,C9100nF/50V MKP
X1connector 2pin
X2connector 3pin
J1-J5FASTON 4,8mm

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