How to assemble 1W audio power amplifier using IC LM 390

Introduction

A simple easy to build audio power amplifiers are always beneficial to novice and small builders for their requirements. Especially battery-operated audio power amplifiers become handy for small projects like radios, music systems, tape recorders, etc. In this category low cost and low component count, audio power amplifiers are popular among electronics enthusiasts. 

In this post, a battery-operated low-cost audio power amplifier using an IC LM390 is described for assembling. Assembling of this circuit is made easy and compact by introducing a readymade PCB design for this circuit design. 

Special features of the circuit design

Battery operation for this circuit is possible since current consumption is restricted as it is an IC-based audio power amplifier. 6V, 7.5V and 9V battery operations are possible based on the usage condition. 

The audio output is around 1W which is sufficient for many domestic gadget applications.

TThe circuit design economizes component count and as such minimum external parts are used along with the IC.

The circuit is capable of various voltage gains ensures low distortion output. 

The gain is set to 20 for optimal performance. The gain can be increased to 200 with suitable external components. 

The IC used here LM390 is a Fourteen pin dual-in-line package.

Applications

This 1W audio power amplifier is mainly used in the following 

AM-FM radio amplifiers 

Portable tape player amplifiers 

Intercoms 

TV sound systems 

Lamp drivers 

Line drivers  

Ultrasonic drivers 

Small servo drivers 

Power converter, etc. 

The circuit schematic

A basic circuit schematic of a 1W audio power amplifier employing a single DIL IC LM390 working on a 6V power supply is given here. 

Practical circuit design

Based on the above design a practical circuit design as it can be directly assembled on a readymade PCB is given. 

Parts list

IC LM 390 -1

R1=390 ohms resistor

R2=2.7 ohm resistor

VOL=10K ohm volume control

C1, C3=0.1MFD capacitors

C2=0.05MFD capacitor

C4=470MFD electrolytic capacitor

LS= 4ohms 1W Loudspeaker (terminal)

S1=on/off switch

Input= Audio signal input

VCC=6V DC

PCB design 

A readymade PCB design specially designed for this circuit is made available for ease of construction. Assembling is made easier by using this PCB design for novice and hobbyists. 

To sum up

IC LM390 based audio power amplifier is a versatile circuit design that suits everyone and every audio-based project.  Please give your comments and suggestions for the benefit of all.